1.which of the following make as yawn?
a. reading a book
b. being in a crowded room
c. being around plants
d. being in a small air-conditioned car

2.what does the word "involuntary" mean?
a. expected
b. unexpected
c. within control
d. uncontrollable

3.which of the following may be a benifit of yawning?
a. it warms us of possible attacks by dog
b. it provides us the carbon dioxide we need
c. it cools our brains
d.it balances the amount of oxygen and carbon dixide
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