Under which of the following circumstances might the president call a special session of congress? a. when congress has just convened a session b. in order to ask congress to consider a particular bill c. as a way to weaken the party in power in congress d. when the house will not consent to adjournment

The correct answer should be
A.when Congress has just convened a session

The president can under certain conditions summon both houses or either of them and it can be for reason that is not about a bill such as help during a crisis or similar things. It is not done to weaken parties in the congress since it has no influence on their power.