OK, like I said yesterday. These are pretty basic and you don't seem to be getting any of this. You will need lots of help. Do not despair because there are plenty of ways you can get this stuff. We all struggle from time to time so don't give up.
First of all the symbol you referred to means perpendicular: horizontal line with a vertical line going through the middle.
That is not correct for #14, the correct answer is C. A median connects the opposite angle to the midpoint of the line segment.
Next answer is: definition of a midpoint (Get it from the above statement)
Next answer should be: C. H is the midpoint of segment EF (Please see the above two statements)
#17: C.definition of a midpoint
#18: A.substitution property of equality (This is an equality statement and none of the other answers make sense. So you can figure this one out by elimination)
#19: B.SAS You have AB congruent to EF, then angle A congruent to angle E, and finally you proved AD congruent to EH. Do you see the reasoning? Side, Angle, Side
Finally #20 is C.CPCTC
Please give me some feedback on if you are understanding my explanations. There are many different approaches to teaching and learning this stuff. So if you aren't clear, put in some work and I'll help.