1.Before leaving the country,the new couple sold their house ____6.000 dollars
A.for B at C on D with
选B at, 以...价售出, 用介词 at, 对应地, 以...价买...为pay $... for sth
2.He based all his arguments ____supposition
A.to B in C on D with
答案没错是 on
具体是要根据该句子意思来的, 这句话的意思是"他把他所有的论点都建立在假设上"
argument to ...
=...的论点
例如类似的to用法, the key to the door = 该门的钥匙