Hacker review of clear sentences

8-1 Active VS. Passive verbs
I learned before, but its also very helpful to let me revise.
8-2 Active VS. Be verb
I understand the difference between active and be verbs.
8-3 Active verbs (edit and compare)
I understand what is active verbs, after I did this exercise.
9-1 parallelism
This exercise help me understand how to make a good sentence.
9-2 parallelism
This part also very helpful.
9-3 parallelism
I understand this part before, but it is still helpful.
10-1  10-2
I know how to avoid adding some meaning use less words, after I did this exercise.
11-1 mixed constructions.
I know this part before, but this exercise help me to revise.
11-2 mixed constructions.(edit and compare)
I know this part before, but this exercise help me to revise.
12-1 misplaced modifiers.
This part help me a lot, and very helpful.
12-2 misplaced modifiers (edit and compare)
This part help me a lot, and very helpful.
12-3Danging modifiers.
This very helpful, and I learn a lot.
12-4 Danging modifiers
This exercise is very helpful.
13-1 Shifts: person and number
I know this part before, but this exercise help me revise a lot.
13-2 Shifts: tense.
I learn a lot from this exercise.
13-3 Shifts
it is not that helpful, but good to know.
13-4 Shifts (edit and compare)
This part is very helpful, I learn a lot from this exercise.
14-1 Choppy sentences.
This part is very helpful, I learn a lot from this exercise.
14-2 Choppy sentence (edit and compare)
This exercise help me a lot.
14-3 Subordination.
This is very helpful for me to learn it, because I do not know before.