[考題] how to do & what to do

[SOSophy (SOSophy)]

題目是 All the children in our school know _________________ during an earthquake.
a) how to do
b) when to do
c) what to do
d) where to do

答案是c 可是為什麼不能a?
麻煩各位高手解答了

手機排版請見諒。

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推 tom91002:爬文"how to do"
→ SOSophy:thx!!!!!!!!!