Ivan Detkov: D19 starts a very unfavorable ko with a risk to lose many points. Saying that I can imagine positions when this is playable. Hence, it looks like B16 is a bad solution here.
posetcay: Yes, I agree that D19 should be the only correct solution here, even though D19 starts a terrible ko for opponent, it is still better to not give the option of choosing. The only counter argument could be that this is a intermediate level collection and B16 is close enough to the correct solution to be accepted.
Djab: I suggest to suppress the mention "No ko" in the title because there is one combinatino where there is no choice but a ko :
B16 - C16 - D19 - B15 (instead of H18) - H18 - J18 and then life is on condition, depending on a ko : am I right ?
d4rkm4tter: After your sequence, black descends h19 and is alive, right? So b15 or h18 doesn't matter black can live both ways.
I flagged B16-D19 as incorrect.