In my textbook there's an exercise where you're supposed to fill in the gaps:
今天的菜____________________到明天就没有人买了。
I'm a bit confused with it. What is meant here by "到明天就没有人买了"?
P.S. The task is to fill in the gaps with 非......不可 construction.
2 Answers
今天的菜 = Today's vegetable
到明天 (reach tomorrow) = when tomorrow come
就没有人(会)买了 = then no one (will) buy it
"今天的菜到明天就没有人买了" is a [(topic) + (comment)] sentence. It is already a complete sentence
今天的菜 (非......不可), 到明天就没有人买了。
The blank space can be filled in with another comment. Logically thinking, what would be the solution to the problem that 'no one will buy the vegetable tomorrow? The answer is "sell them all today"
so, the missing part of '非(......)不可' is '(在今天內賣掉)'
[非(......)不可] = [must (......)]
Topic: 今天的菜 (today's vegetable)
comment 1: 非在今天內賣掉不可 (must be sold within today)
comment 2: 到明天就没有人买了。 (No one will buy it tomorrow)
Complete sentence: "今天的菜非在今天內賣掉不可, 到明天就没有人买了"
both comment 1 and comment 2 are descriptions about the topic
If you are constructing the sentence on your own, you can refine the sentence more by joining the two comments into one with a conjunction 否則
"今天的菜非在今天內(全部)賣掉不可, (否則)(等)到明天就没有人买了"
I think you are meant to fill something like this：
今天的菜非卖掉不可， （否则）到明天就没有人买了。
到明天就没有人买了 here implies that the vegetables might go stale and no body wouldn't buy it. That's why you have to make sure you sell them all out today -- 今天的菜非卖掉不可.
