Correct Answer: 39

Solution : Let B's efficiency be $x$.
A's efficiency = $2x$
Work done by A and B together in 13 days = 1
Work done by A and B together in 1 day = $\frac{1}{13}$
Work done by A in 1 day + Work done by B in 1 day = $\frac{1}{13}$
⇒ $2x+x=\frac{1}{13}$
⇒ $3x=\frac{1}{13}$
⇒ $x=\frac{1}{39}$
Work done by B in 1 day $=\frac{1}{39}$
Therefore, the work is completed by B in 39 days
Hence, the correct answer is 39.

Correct Answer: Serious

Solution : The correct option is the first option.

Explanation:
The tone of the speaker is serious as it discusses various factors influencing subway air pollution, particularly focusing on the sources of particulate matter, health risks for subway workers, and the mix of particles within the subway system.

The language used is factual and analytical, examining the potential health impacts without conclusive evidence and citing observations and studies. There's a sense of concern and caution regarding the potential health risks associated with subway air pollution, which contributes to an overall serious tone in the passage.

Therefore, the correct answer is serious.

Correct Answer: (2)

Solution : The error is in the second option: to themself.

"To themself" is the part of the sentence that contains an error. The correct reflexive pronoun for "they" is "themselves", not "themself."

The preposition "to" is also changed to "upon" to fit in with the meaning of the sentence, conveying that the subject of the sentence is responsible for causing a disaster, and they did so to themselves.

Therefore, the correct sentence is: "They brought upon themselves this disaster".

Correct Answer: 3

Solution : The correct answer is the third option.

"Reduce" implies a conscious effort to decrease the amount of fat, which fits the context better.

"Cut" could imply a sudden or drastic reduction, while "lose" is generally associated with weight loss rather than managing dietary fat.

Therefore, the correct statement should be: "Try to reduce the amount of fat in your diet."

Correct Answer: (3)

Solution : The correct choice is the third option.

The word "than" is typically used for making comparisons, but in this context, the sentence expresses a sequence of events. First, they reached the platform, and then the train came in. The word "hardly" is followed by "when", as they are correlative conjunctions.

Therefore, the correct sentence is: We had hardly reached the platform when the train came in.

Correct Answer: Swaran Singh Committee

Solution : The correct answer is the Swaran Singh Committee.

At the recommendation of the Swaran Singh Committee, the Fundamental Duties were incorporated into the Constitution. Initially, the Indian Constitution did not outline a specific set of responsibilities for its citizens. However, in 1976, with the enactment of the 42nd Constitutional Amendment, this was rectified.

Correct Answer: Mount Everest

Solution : The correct answer is Mount Everest.

Mount Everest has its latitude within one degree of New Delhi. The latitude of New Delhi is 28.7 degrees N and 77.1 degrees E and the latitude of Mount Everest is 27.9 degrees N and 86.9 degrees E. Bahut New Delhi and Mount Everest lie in the Northern Hemisphere. Mount Everest is the highest mountain in the world and it is located on the border of China and Nepal with an altitude of 8848.86 metres.

Correct Answer: Himachal Pradesh

Solution : The correct option is Himachal Pradesh

Kardang Monastery is situated in the Indian state of Himachal Pradesh. Kardang Monastery is a Tibetan Buddhist monastery located in the Lahaul and Spiti districts of Himachal Pradesh, India. It is one of the largest and oldest monasteries in the region, situated at an altitude of about 3,500 metres (11,480 feet) above sea level.

Correct Answer: 40

Solution : In a column, find the square of the first number to get the second number and then multiply the first number by consecutive natural numbers(starting from 3) to get the third number.

In the first column: 6² = 36 and 6 × 3 = 18
In the second column: 7² = 49 and 7 × 4 = 28
Similarly, in the third column: 8² = 64 and 8 × 5 = 40

So, 40 is the missing number in the given figure. Hence, the fourth option is correct.

Correct Answer: 1 : 2

Solution :

$\angle$ BAC = $\angle$ QPR
$\angle$ ABC = $\angle$ ACB and $\angle$ PQR = $\angle$ PRQ
$\angle$ ABC = $\angle$ ACB = $\angle$ PQR = $\angle$ PRQ
$\triangle$ BAC ~ $\triangle$ QPR
$\frac{area(\triangle BAC)}{area(\triangle PQR)}$ = $\frac{h^2}{H^2}$
⇒ $\frac{1}{4}$ = $\frac{h^2}{H^2}$
⇒ $\frac{h}{H}$ = $\frac{1}{2}$
Hence, the correct answer is 1 : 2.