请问this is hard work 和 this is a hard work 有何区别

请问this is hard work 和 this is a hard work 有何区别 This is a hard work this is ____ ,so we must ____ on it.A.a hard work;hard work he is work hard 和he is works hard 和he works hard有什么区别、、 She is going to work hard at English this term.对work hard at she is going to work hard at English this term 对work hard at it is a hard work还是it is hard work This is ( ) hard work that nobody can do it well This is hard work.(改为感叹句,用两种句型） 请问是Making money is hard work对还是Making money is a hard work i still work hard 和I work still hard 有何区别! learning is（ ） 填a hard work还是hard work