Answer:
"writing must make sense to the reader" means that the reader must be able to understand what you are writing. The writing should be clear and understandable. When writing, don't let all of the crazy out of you because your writing might not make sense when you go all out. Read over your writing and play the reader. Become the reader and read over your paper and ask yourself this question, "Does this writing make sense or should I change a few things?" This helped me, I hope this helped you!
OK:
Time flies by so fast.
Does this make sense? Yes! Many people heard this phrase, it is easy to understand.
Not Ok:
Fruit flies like a banana.
Does this make sense? No! Even I have no idea what this means, not many people understand this. And wait, can fruit really fly?!
Hope this helped! Have a good day!