Your classmate has written to invite you to his or her birthday party. write back to him or her
giving
reasons
why you can't
attend the birthday party.

This question does not have a specific answer, nor does it elaborate further into the question, so I will provide an answer that may or may not be approximately what the question is asking.

Dear [classmate’s name],

I would love to attend your birthday party, but unfortunately I won’t be able to. The reason for this is because [state the specific reason why you are unable to attend the birthday party]. Happy Birthday!

From your classmate,

[your signature]

faulty parallelism is a construction in which two or more parts of a sentence are equivalent in meaning but not grammatically similar in form.

the correct version of this faulty parallelism in the sentence is:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.

the problem is the last sentence, the first two have a basic subject+verb+object structure.

so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in all three sentences:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.

umm of course in fact ur getting your answer : )