2道英文選擇題,簡單說下原因

題目：

2道英文選擇題,簡單說下原因
56,If we work with a strong will,we can overcome any difficultly ______ great it is!A,what B,how C,however D,whatever 57,I am going to the post office.______ you are there ,can you get me some stamps?A,as B,while C,Because D,if

解答：

56,If we work with a strong will,we can overcome any difficultly ______ great it is!
C,however 是副詞 修飾 形容詞 great 引導讓步狀語從句 = no matter how
57,I am going to the post office. ______ you are there ,can you get me some stamps?
B,while 當...的時候.