You must know how to attempt A-R type quetions to stand a chance.
In biology and chemistry no extra theory is reuired but in Physics you should read the NCERT textbooks to have an in depth theory knowledge. In physics too the second book of both 11th and 12th are important as theory topics and must be read thoroughly. What I would advise is that you should convert as many as ARs into numericals as possible. That increases speed and accuracy because we are more comfortable handling numbers rather than the confusing language given to us in the question.
I also developed a strategy to reduce silly errors. Click on the image below to get a bigger image
The step where you decide that whether the assertion is right or wrong is the most crucial and increases your chances of getting the right answer to 50 %