涂一涂，分一分。
为提高树木的成活率，园林工人常常给树木输液（主要成分是水和无机盐）．你认为输液管的枕头必须插入到树干的（ ）
— Dad, I don't think we can go into the building. Look at the sign — “_______”.
— Oh, I didn't notice it.
