题目内容：

Scientists have learnt a grate deal about the kinds of food people need.

优质解答

deal n. 许多

a great deal 许多, 大量(代替不可名,可作宾语)
The place changed a great deal and was almost unrecognisable.
这个地方变化很大,几乎认不出来了.
来自《简明英汉词典》

a great deal of+不可名, 许多/大量.
They absorbed a great deal of the Roman culture.
他们大量地吸收了罗马文化.
来自《简明英汉词典》

句意: 科学家已经了解了关于人们所需要的食物种类的大量情况.