[求助]做小安阅读发现有句话理解不了，请友友们帮助一下~

  阅读： Now Congress, in apparent agreement, has required by law that businesses awarded federal contracts of more than $500,000 do their best to find minority subcontractors and record their efforts to do so on forms filed with the government.

问题：

The passage supplies information that would answer which of the following questions?

(A) What federal agencies have set percentage goals for the use of minority-owned businesses in public works contracts?

(B) To which government agencies must businesses awarded federal contracts report their efforts to find minority subcontractors?

(C) How widespread is the use of minority-owned concerns as “fronts” by White backers seeking to obtain subcontracts?

(D) How many more minority-owned businesses were there in 1977 than in 1972?

(E) What is one set of conditions under which a small business might find itself financially overextended?

我做这个题的时候，是定位到上面的这句话，于是选了c，因为我理解businesses需要report给congress，虽然我现在理解了congress只是要求，而不是report的对象，但是还是没办法理解这句话 Congress， in apparent agreement, has required by law that。。。

是congress被law要求，that后面是law的内容吗，但是为什么没有has been被动用法？