如题所述
1. be+doing：构成进行时态，有现在和过去两种进行时态。如：
The girls is reading and copying the new words now.
2. be+going to do，表示"打算或将要做某事"，be有现在和过去两种形式。如：
We are going to plant trees in the park.
I didn’t know if she was going to come here.
3. be+to do，表示"按计划安排将要做某事"。如：
The new shop is not to be opened till next Monday. One night an angel came
to
Mary and told her that she was to have this special boy.
The girls is reading and copying the new words now.
2. be+going to do，表示"打算或将要做某事"，be有现在和过去两种形式。如：
We are going to plant trees in the park.
I didn’t know if she was going to come here.
3. be+to do，表示"按计划安排将要做某事"。如：
The new shop is not to be opened till next Monday. One night an angel came
to
Mary and told her that she was to have this special boy.
温馨提示：答案为网友推荐，仅供参考
第1个回答 2016-05-27
动词的现在分词和被动态前面用be动词
第2个回答 2016-05-27
第3个回答 推荐于2017-12-15
非谓语动词如：to do、doing、done前面需要加be动词构成时态或是被动语态或者动词不定式表示特定意思。
解析：be动词和非谓语动词一起构成句子的谓语；其中be动词是助动词，不是表示系动词“是；成为“的意思。
例如：
The little girl is talking pleasantly with her mother.
小女孩正跟她妈妈愉快地交谈着.
分析：这里的be（is）和talking构成现在进行时，表示正在进行。
It seems to be a Chinese tradition to haggle over the price of virtually anything that is bought.
中国的传统似乎是差不多任何可以购买的产品都可以讨价还价。
分析：这里的be（is）和bought（buy的过去分词）构成被动语态，表示被买。
So his solution was to build Voyager almost completely out of new materials.
所以他的解决方案是几乎完全用新型材料来打造“航行者”号。
分析：这里的be（was，be的过去式）和动词不定式一起做句子的谓语，表示将要去做什么。
I am going to justify that soon. It could be minimum or maximum.
等下就会来证明这个，这个可以是最小值或者最大值。
分析：这里的be（am）和going to+动词原形构成一般将来时，表示计划，打算的意思。本回答被网友采纳
解析：be动词和非谓语动词一起构成句子的谓语；其中be动词是助动词，不是表示系动词“是；成为“的意思。
例如：
The little girl is talking pleasantly with her mother.
小女孩正跟她妈妈愉快地交谈着.
分析：这里的be（is）和talking构成现在进行时，表示正在进行。
It seems to be a Chinese tradition to haggle over the price of virtually anything that is bought.
中国的传统似乎是差不多任何可以购买的产品都可以讨价还价。
分析：这里的be（is）和bought（buy的过去分词）构成被动语态，表示被买。
So his solution was to build Voyager almost completely out of new materials.
所以他的解决方案是几乎完全用新型材料来打造“航行者”号。
分析：这里的be（was，be的过去式）和动词不定式一起做句子的谓语，表示将要去做什么。
I am going to justify that soon. It could be minimum or maximum.
等下就会来证明这个，这个可以是最小值或者最大值。
分析：这里的be（am）和going to+动词原形构成一般将来时，表示计划，打算的意思。本回答被网友采纳
