The correct answer is: A. to be cautious.
The phrase “to take it lying down” means to accept something without complaint or resistance. In this context, the party stalwarts are advising the President to be cautious and not to react to the recent criticism he has received. They are suggesting that he should wait until the situation has calmed down before making any public statements.
Option B is incorrect because being on the defensive means to be ready to defend oneself against attack. This is not what the party stalwarts are advising the President to do. They are not suggesting that he should attack his critics, but rather that he should be careful not to say anything that could make the situation worse.
Option C is incorrect because taking rest means to relax and recover from fatigue. This is not what the party stalwarts are advising the President to do. They are not suggesting that he should take a break from his duties, but rather that he should be careful not to react to the recent criticism.
Option D is incorrect because showing no reaction means to not express any emotion or feeling. This is not what the party stalwarts are advising the President to do. They are not suggesting that he should pretend that he does not care about the criticism, but rather that he should be careful not to say anything that could make the situation worse.