Who is the head of the executive branch in a parliamentary system

I think the prime minister is the head of the executive branch in a parliamentary system.

it is the prime master.  the prime minister and other officials appointed from the parliament make up the executive.

i truly dont know the answer wait i do its 1,3,4

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."