Although the first part of the book is easy ,the rest ____谢谢了,大神帮忙啊A has proved difficult 为什么选A这个选项难道没有问题么 为什么不是has been proved to be difficult

although the first part is easy ,the rest are difficult是什么意思 at first与at the first的区别另at first可以用在句中吗?eg:Although it made me not feel well at first,yet . Although we made the time a little( )we missed the first bus because of the bad weather A (p )is the first person to do something this is the first p--- of Huanhuan'letter At that speech contest,he won the first p（ ）. 英语翻译as Hitler thundered against Poland,Denmark,Norway,the American spirit hardened.(Although the first impulse of Americans had been to stay out of the conflict) Could I take the book out of the library, Mr, Wang ?No, （）you pay 50Yuan first. A, if B, unless C, because D, although Tom works very hard at his lessons.He did not get the first in the exam.A.however B yet C.though D although the first The first 英语翻译rtAnd although he now walks and walk and talks the talk,at first his father’s great obsession seemed ridiculous. although 18.Although the first pulsar,or rapidly spinning collapsed star,to be sighted was in the summer of 1967 by graduate student Jocelyn Bell,it had not been announced until February,1968.(A) Although the first pulsar,or rapidly spinning collapsed star,to John got the first prize in the contest.His parents were p of him 英语翻译Although Seebeckobserved thermoelectric phenomena in 1821 and Altenkirch defined the ZT equation in 1911,ittook several decades to develop the first functioning devices in the 1950s and1960s.4 They are now called the firstgeneration therm _____the heavy traffic jam,john got to the place where the conference was held on time.in ____,he was the first one who came to the conference.第一空填though 还是although,第二空填什么? 主谓一致 14. Although the first part of the book is easy, the rest ______.B. has proved difficult C. is supposed difficult 为什么选B不能选C 谢谢