In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[Q]: Autism is _ to four times more likely to affect boys than girls.
[A]: three


[Q]: Pets also track in pollen, and _ out of every ten people is allergic to cat or dog dander.
[A]: one


[Q]: Educational psychology addresses the topic of learning by studying _ aspects of learning.
[A]:
three