Being good to the old people is necessary for us.（同义句）—is necessary for us — — good to the old people .The word“o—”means “happen”.（写单词）
问题描述：
Being good to the old people is necessary for us.（同义句）
—is necessary for us — — good to the old people .
The word“o—”means “happen”.（写单词）
答
to be
occur
答
It is necessary for us to be good to the old people.
occur=happen
答
1 It to be (it的一个句型 it be adj+for sb.+to do sth)
2 occur
[əˈkə:]
vi.
发生; 举行; 存在