Correct Answer: Frightful

Solution : The correct choice is the first option.

Ferocious: This term describes something or someone that is extremely fierce, violent, or savage in behaviour. It often implies a high level of aggression or intensity.

Frightful: This is the correct synonym for "ferocious." It describes something causing fear, terror, or apprehension, aligning with the intense and aggressive nature associated with "ferocious."

The meanings of the remaining options are as follows:

Mild: It means gentle, moderate, or not intense.

Conscientious: It refers to somebody who is diligent, careful, and meticulous in his work or duties.

Tame: It means domesticated, gentle, or lacking wildness.

Therefore, the closest synonym for ferocious is frightful, as both convey a sense of intensity and something causing fear or apprehension.