Studio Classroom

a. doing it b. to do it c. to doing it d. it to do

Explanation

疑問詞 how 後面接不定詞（to V）表示「要怎麼做這件事」，這裡的 how to do it 為名詞子句，作動詞 know 的受詞，正確答案為 B。

Changing a light bulb is easy. Don’t you know how ______?