Both the parents and the children are here.

ii. A、B表示同一個人、物或者觀念的時候，謂語動詞要用單數形式

A journalist and author lives in the sixth flat.

The turner and fitter is under twenty-five.

iii. And連接幾個單數主語，主語由each、 every、 no、 many a等詞修飾的時候，謂語動詞要用單數

Each boy and each girl is invited.

Every boy and girl is invited.

No boy and no girl is there now.

iv. A、B為兩個不可分的東西時，謂語動詞用單數

A law and rule about protecting environment has been drawn up.

Bread and butter is nutritious.

b) 由or, not only… but also …, either… or …, neither… nor …連接主語時，謂語的人稱和數與靠近的主語一致 (注意，敘述句和疑問句隨語序不同而不同)

Either you or I am mad.

Neither you nor he is naughty.

Not only the farmer but also his family were friendly to me.

c) 當主語后跟有with, along with, together with, besides, except, like, including, as well as, rather than等詞的時候，謂語動詞不受詞組的影響，僅和主語保持一致

All but one were here just now.

A library with five thousand books is offered to nation as a gift.

2. 單一主語的情況

a) 以復數形式結尾的統稱名詞作主語時，例如physics, maths, economics, news, means, works, 等一般在謂語動詞中用單數形式, 當然，若表示復數的意思則另當別論

Physics is very important.

Every means has been tried.

b) 當由至少兩個部分組成的工具的名稱，或者衣服的名稱等作主語時，例如trousers/pants, shoes, glasses, scissors, goods, clothers等，謂語用復數形式;如果這些詞由Pair(suit, piece, series,kind)+ of修飾的時候，謂語動詞要用單數

My trousers are white and his clothes are black.

A pair of scissors is lying in that drawer.

但是在these/those pairs (…) of + 復數名詞之后，謂語動詞則用復數形式

These kinds of glasses are popular this summer.