【助動詞の解答】
 １．
　⑴ I  can  play  the  piano. 
　⑵ You  may  go  out.
　⑶ She  will  be  busy.   ＊　is の原形は 
　⑷ He  must  study  English  every  day. 
　⑸ We  should  do  our  homework  before  dinner. 
　
２．
　⑴ ア 彼女は今日ここへ来るでしょう。 
　   イ She  won't  come  here  today. 
　   ウ Will  she  come  here  today? 
　       Yes, she  will.  /   No, she  won't. 

　⑵ ア あなたは上手にスキーをすることができる。 
　   イ You  can't  ski  well. 
　   ウ Can  you  ski  well? 
　       Yes, I  can.  /  No, I  can't. 
　       
　⑶ ア ナンシーはその辞書を使ってもよろしい。 
　   イ Nancy  may  not  use  the  dictionary. 
　   ウ May  Nancy  use  the  dictionary? 
　       Yes,  she  may.   /   No, she  may  not.（No, she  mustn't.） 
　       
　⑷ ア 彼はラジオを聞かなければならない。 
　   イ He  mustn't  listen  to  the  radio. 
　   ウ Must  he  listen  to  the  radio? 
　       Yes,  he  must.  /  No, he  doesn't  have  to. 
　       
　⑸ ア 彼は５時に出発する予定です。 
　   イ He  isn't  going  to  leave  at  five. 
　   ウ Is  he  going  to  leave  at  five? 
　       Yes, he  is.  /  No, he  isn't. 
　       
　⑹ ア 彼女は上手にテニスをすることができるようになるでしょう。 
　   イ She  won't  be  able  to  play  tennis  well. 
　   ウ Will  she  be  able  to  play  tennis  well? 
　       Yes, she  will.    /   No, she  will  not. 
　       
　⑺ ア 彼は英語で手紙を書かなければならなかった。 
　   イ He  didn't  have  to  write  a  letter  in  English. 
　   ウ Did  he  have  to  write  a  letter  in  English? 
　      Yes, he  did.   /    No, he  didn't. 

３．
　⑴ I  am  going  to  watch  TV. 
　⑵ You  have  to  be  kind  to  old  people. 
　⑶ You  were  able  to  arrive  at  the  party  by  three.　＊　by「～までに」 
　⑷ Are  you  going  to  be  busy  tomorrow?
　⑸ Do  I  have  to  get  up  early? 
　⑹ Where  are  you  going  to  play  baseball? 
　⑺ What  do  I  have  to  do? 
　
４．
　⑴ He  will  be  able  to  ride  a  bicycle.
　⑵ She  could  cook  very  well. 
　   She  was  able  to  cook  very  well. 
　⑶ You  will  have  to  go  to  see  Mr. Brown. 
　⑷ I  had  to  answer  the  question.

５．
　⑴ Shall  we
　⑵　Will  you 

６．
　⑴ You  must  be  tired. 
　⑵ He  may  be（an）American.
　⑶ You  mustn't （may  not） go  there.
　⑷ You  don't  have  to  cook  dinner. 
　⑸ Will  you  help  me? 
　⑹ Shall  I  open  the  door? 
　⑺ I’d  like  to  go  shopping. 
　⑻ Would  you  like  another  cup  of  coffee?