Two students in the group make predictions about the motion of rocket Y compared to that of rocket X. Their arguments are as follows.

Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. the winds blow from west to east in jet streams but the flow often shifts to the north and south. jet streams follow the boundaries between hot and cold air. the earth's rotation is responsible for the jet stream as well.

This is the answer: body 1 + engine 2