5) If Design wanted to change this card's rules text but keep it a hybrid card, which of the following options would not work?
a) flash; shroud
b) double strike
: Target player discards a card. Activate this ability only any time you could cast a sorcery.– CORRECT
Number 5 I don't have a big problem with, but I wanted to point out an easy mistake you could make in thinking about it. They want a hybrid card, not a gold card. A black 1/4? yuck. But a black / white 1/4 that makes you discard... well it's acceptable, at least. Meanwhile a flash shroud 1/4, or a doubestrike 1/4, those are both too monocolored to be gold. Same can go for c or d. They are all really monocolored cards as 1/4s. (blue, white, blue, white, respectively). So while I can't argue strongly that e is wrong, the question overall seems pretty weak to me, as it's too easy to consider a, b, c, and d as monocolored cards. Hybrid treads a thin line between monocolored and gold, so they're some of the hardest cards to design.
6) Design often makes creatures that have flash and "enters the battlefield" triggered abilities like Deflecting Mage. Which of the following abilities would we least likely pair with flash?
e) Target creature gets +3/+3 until end of turn. – CORRECT
The claim WotC makes here is that "e) is the only "enter the battlefield" effect you would ever see of the above on a creature that didn't have flash" and therefore the least likely to be paired with flash. I don't think that's accurate at all. Exhibit A: Briarhorn - the likelyhood of e+flash = 100%. It was done, and not in ancient history, but recently, in a block I would consider part of modern design. Answers a and d are seen often enough, both as recent or more recently than e in one form or another. This leaves b and c. Neither has been done yet, though Bogarden Hellkite is a superset of c. Clearly they cannot be done without flash, but that doesn't mean any design team should hand them off to development. Their "likelihood" seems pretty low to me. I could see b as a cool new uncommon or rare cheap red creature. If I wanted to design c I would be much more likely to design a white creature with flash, 2 power, and that either has first-strike or gives itself first-strike when it enters the battlefield.
Overall I can see the argument for b or c, but not e. Also b and c are so close for me that I wouldn't put them together in this question.
19 and 20 use this card: