【糖衣】評論
average平均(v.)是指 the amount的平均, 因為the amount是單數，單數後面的動詞要有s, 所以選(B) averages 他們可以存到的數量平均是6345元一個月
【Jing-ching Ch】評論
Average 這裡是名詞可數Example:Parents spend an average of $300 a year on toys. the amount they can save (29) just 6,345 NT a month.
【yee1221】評論
the amount (which) they can save averages just 6,345 NT a month.