e going to 表示近期、眼下就要发生的事情,will 表示的将来时间则较远一些,如：
He is going to write a letter tonight.He will write a book one day.
2.be going to 表示根据主观判断将来肯定发生的事情,will表示客观上将来势必发生的事情.
He is seriously ill.He is going to die.He will be twenty years old.
3.be going to 含有“计划,准备”的意思,而 will 则没有这个意思,如：
She is going to lend us her book.He will be here in half an hour.
所以本题选will,羊年属于客观上势必发生的事