The first sentence should read 'The phone rings early in the morning.' because the subject is singular and the verb rings agrees in its third person singular form.
The second sentence should read 'They sit on the wall after school.' because the subject is plural and the verb sit agrees with the third person plural form.
The third sentence should read 'The bad falls out of my hand because it is heavy.' because the subject is singular and the verb falls agrees with the third person singular form.
