Question

when a police arrive the crowd dissapear covert into simple​

Answer 1

Answer:

As soon as the police arrived,the crowd disappeared.

Answer 2

Answer:

As it is time clause

Explanation:

We can convert the sentence into simple sentence either by present participle or by perfect participle

Formation of present participle

[M.V.(ing form)+object/other+Sub+verb+Obj/other]

According to the formation of present participle

This is will be in the formation like this

• Disappearing of crowd when a police arrived

Now it can be also done with this formation

[Having+past participle+Obj/other+sub+verb+Obj/other]

According to this

Having dissappeared when a police artived