1.It was not until dark ___ he found ____ he considered the

1.It was not until dark ___ he found ____ he considered the correct solution to the problem.
A.when that B.that what C.when what D.that that
2.The shoes in the shoe shop ____(vary) in size,color and shape.
第一题答案是B,为什么?我选择的是D.condsider后面不是有宾语了吗?再加what上去干什么?怎么翻译?