hi Sindhu,

First of all i would like to give you brief idea of B.TECH programe,

there is a lot of stream in btech programe like

1)CSE(Computer Science Engineering)

2) Mechanical Engineering

3)Civil Engineering

4)Electrical Engineering 

5)Chemical Engineering

And etc.

Now let's come to the point that what course should you study before going into a btech programe.

So,

for the CSE you have to focas on the Mathematics also touch with the some programe language like C language,C++, and many mare.

For the mechanical Engineering you have to focus on the Physics in which you have to focus on these topic like Thermodynamics,Kinematics, etc.

For the Electrical Engineering you have to focus on the Physics in which you have to focus on these topic like Electric circuit  etc.

For the civil Engineering you have to focus on the mathematics in which you have to focus on these topic like height and distance etc.

For the chemical Engineering you have to focus on the organic chemistry.

hope it will help to choose your way.

thanks