1.順便拜訪
2.B.when可以指時間點或者時間段,由when引導的時間狀語從句,主句用過去進行時,從句應用一般過去時
3.C.not until指直到……才……,后面的Chinese people took on a new look缺少了時間狀語,用when
4.converse指交談,不及物動詞,protect指保護,及物動詞.你應該想問conserve和protect之間的區(qū)別吧.
（下面是轉載網(wǎng)上的詳細解答）protect用作及物動詞,意為“保護,保衛(wèi),防護”（to keep someone or somthing safe from harm,damage,or illness),用于使人或物免受任何危險、侵襲或傷害,適用范圍廣泛.
如：protect one's country,(one's sister,one's head,the townspeople,one's interest)等,并常用protect...from 結構.
如：Try to protect your skin from the sun.
A helmet protects your head from injuries.
He raised his arm to protect his child from hurting.
conserve一般說保護自然資源,是指通過有準備、有計劃的、明智的方法來保護事物處于安全,防止改變或損壞,如保護人等的權利,義務等
We must conserve our forests if we are to make sure of a future supply of wood.
如果我們想確保未來的木材供應,就必須保護森林.
"People have to learn to conserve water anytime,especially during the drought."
"大家必須學會節(jié)約用水,特別是在干旱期間."