助動(dòng)詞be 和系動(dòng)詞be 的區(qū)別 在語法書上,非謂語動(dòng)詞的不定式部分介紹說：系動(dòng)詞be+不定式作表語和
在語法書上,非謂語動(dòng)詞的不定式部分介紹說：系動(dòng)詞be+不定式作表語和 助動(dòng)詞be+不定式做表語有區(qū)別 然后舉了例子
1.系動(dòng)詞be+不定式作表語：You're not to smoke in the office.
He felt excited because he was soon to go abraod travelling.
2.助動(dòng)詞be+不定式做表語:My dream is to be a doctor
Mary's task is to set the table.
但是系動(dòng)詞be+不定式作表語和 助動(dòng)詞be+不定式做表語 這兩種形式中,是怎么樣區(qū)別的be什么時(shí)候是助動(dòng)詞什么時(shí)候是系動(dòng)詞的呢?請(qǐng)幫忙結(jié)合上面的句子分析一下,