The correct answer is B) control the strategy of the party.
The leader of a political party in the legislative branch has the power to control the strategy of the party.
That is why it has the power, the faculties and is the leader of the party. They are representing the interests of the people who voted for them and most importantly, the interest of the citizens of the United States. So the leader of the party must have in mind the big responsibility it has when discussing, debating and voting for a new law. This leader has to establish a good strategy for the other members of its party to follow and present a common front during debates.
The other options were a) nominate various officials, c) select state and national judges and d) decide how members will vote.