1,The number of the students in our class is much large than in your class
2,The shop sold guangdong food is on the other side of the road.
3,My brother has joined the army since he graduated from school
4,He asked how long the noise made me wake last night
5,Can you believe in such a richcountry there's so much population.

(注：告诉我错误的原因及其中的语法，谢谢了！）

1,The number of the students in our class is much large than in your class ．（缺少另一个比较，应在large 前that指代＂你的＂班级的人数．为什么要用that呢？因为that=the number of the students (in your class).但为避免重复，所以用that指代）
2,The shop sold guangdong food is on the other side of the road. （分析一下句子：这里出现了两个谓语了，可变为一个定语从句．定语部分为：＂卖广东食物的＂．动词sold应改为sells.因为商店销售的是广东食物，表明它不是发生在过去的．后面is有提示）
修改后：The shop which sells guangdong food is on the other side of the road.
3,My brother has joined the army since he graduated from school （规律：现在完成时的句子中出现since/for,句中的谓语动词要用延续性动词，这题有很多改法）
修改后：My brother has been a memeber of the army since he graduated from school./My brother has been in the army since he graduated from school.
4,He asked how long the noise made me wake last night
He asked how long the noise made me awake last night.
5,Can you believe in such a richcountry there's so much population（这里为believe后接宾语从句，从句部分是there's so much population,调换一下语序.that可省略）
修改后：Can you believe (that）there's so much population in such a rich country？