Can you figure out the correct answer?

Question

A study attempts to determine whether a football filld with helium when kicked travels farther than one that is filled with air. each subject kicks twice- once with a football filled with helium and once with a football filled with air. The order of the type of football kicked is randomized. This is an example of :

a. matched pairs experiment

b. a double blind observational study

c. a satisfied analysis

d.the placebo effect

Answer 1

A.  For it to be B the the people choosing the ball to be kicked and measuring the results would also not know which balls had helium and which had air.

Answer 2

i know its NOT D.

i would guess A. or B.