The book, the subject of which is B, is good for reading.

Nice test coz i've got 10! Thank for the post.

Just change "crossed out" to" cross out". We should use the base form of the verb when it is with auxiliary "do". Everything else is correct.

Oh I'm sorry, but I also committed typo error! It should be "I had an observation" instead of " I have some an observation."

I got a perfect score! That was a good test, but i just have some an observation about typo error. Thanks anyway!

If you are just choosing which is correct between the two sentences above, sentence #1 is the correct one since sentence #2 is unbalanced and doesn't follow parallelism. In the case of how "to' is used in sentence #1, it is not

I have encountered the word "Informatics" because we have chains of computer schools here named as Informatics Computer Institute which we simply call as Informatics, for short.

Ha ha! I got 2 mistake. The answer for #1couldn't possibly be " must have dressed "? Anyway, thanks for the post!