1. There is a chance Dr. Li will be able to be back for May Day.

按我理解，这句话省略了chance 后的 that。而that后所跟的短句是there be 句型中的实质主语。同时也是个修饰chance的定语从句，请问这个理解对么？

【答】这里的(that) Dr. Li will be able to be back for May Day 是同位语从句，不是定语从句。

2. There are lots of people who can actually help you.

请问这句话中的 who 能否省略？

【答】 who can actually help you 是定语从句。如果定语从句的先行词是 there be句型的主语，则定语从句的主语可以省略。所以这句话中的 who 能省略。

3. There is possibility we'll go, all depends on the weather.

请问这句话该如何分析？能否体现上述原则？

【答】 we'll go = that  we'll go,是同位语从句，作possibility的同位语。同位语从句的引导词 that  通常不省略，但是有时候可以省略。最好是不省略。There is possibility we'll go, 和all depends on the weather.是并列句。