Three years later another boundary was discovered that between the mantle and the Earth's crust.
问题描述：
Three years later another boundary was discovered that between the mantle and the Earth's crust.
从句中怎么没谓语呢
答
People discovered it between the mantle and the Earth's crust.句中的 that between the mantle and the Earth's crust.是主语another boundary的补足语,加上that是为了不让人理解为 was discovered 的地点状语....