—IheardthatmanypeopleplantedtreesonTreePlantingDaywitho...

問題詳情：

—I heard that many people planted trees on Tree Planting Day without stepping out this year. I wonder    ▲    .

—They did this by taking part in“cloud planting" on the Internet.

A. what they did        B. how they did that     C. why they joined the activity

【回答】

B

知識點：賓語從句

題型：選擇題