英文超級高手請進、、、

He is in his room, playing his drums himself.
They......., must been is wrong because after a "," there shoule be a linking word like 'and' 'or' 'but'
Another reason is that no one will asept it.
'Another is that' is wrong because ANOTHER is an ADJECTIVE so there is no subject in the sentence.
The poorest country in the world is Luxembourg.

Lastly , examples:
We spent two days repairing the car.
It is no use arguing with the other driver.

Verb+to which MUST use gerund:
led to
be used to
devoted to
pay attention to
confined to
in addition to
accustomed to
confessed to
beneficial to

I don't know what's mean錯或對and有或無

1.1 He is over there, playing his toys with his friends.
1.2 They are looking tired, must have been working so hard.

2.1 It's should be "Another reason that is", 因為在英文每逢陳述句時， is / are 一定放在後面。如果是例如 "is that" 的話，就是問題。
2.2 如上， It's "Another that is"

3.1 Poorest 應該有，是指 "最貧窮" / "最差" ，Poorest 前面一定有 "the"

4 不知道你想問怎麼？