They must ----- (promise) ------ (look) after them well
问题描述：
They must ----- (promise) ------ (look) after them well
答
promise to look
答
promise, to look
答
事情发生后promise;looking
之前还没照顾用to do
答
They must --promise--- (promise) --to look---- (look) after them well
答
They must promise to look after them well.
他们必须承诺（发誓）要好好照顾他们. promise to do sth,承诺/发誓/答应做某事