Can someone plz help only if you know all the answers!!! Plzz this is like my 4th time asking

d. the polar jet stream   lies between the polar easterlies and trade winds should be your answer

answer; randomized controlled trials;

answer; (d) they are in charge of the ushers and making sure the audience gets to their seats on time; they also control the box office; i know (c) is wrong and (b) don't make sense;