I think all of them are similar to A because they all are the same shape
The first flip can obviously return only H or T.
Suppose the coin lands on H. This means that every following string is possible (and thus part of the sample space)

So, there are 16 such strings, because every flip has two possible outcomes.
Suppose now the coin lands on T. Like before, we add to the sample space the following strings:

And thus there are 4 such strings, because we have two choices for each of the two flips.
So, the sample space has 20 outcomes:
H - HHHH
H - HHHT
H - HHTH
H - HHTT
H - HTHH
H - HTHT
H - HTTH
H - HTTT
H - THHH
H - THHT
H - THTH
H - THTT
H - TTHH
H - TTHT
H - TTTH
H - TTTT
T - HH
T - HT
T - TH
T - TT
The answer is D. a quadrilateral with one pair of parallel sides
Since two of the sides are perpendicular that means they both have a right angle so the correct answer is C.