The question setter has fallen into something of a trap here. 'Polyanthus' does indeed mean 'many flowers', but so does Floribunda, which is a cultivar (type) of rose. The former is from the Greek, while the latter is from the Latin.
Generous question askers may have allowed "Floribunda" as an alternative answer, had they had the relevant knowledge. But if this had been the answer that the setter was looking for, the question would probably have been worded more carefully: for example, "The name of which cultivar of a popular garden flower ... "
The safest way to ask this question would of course be to specify whether you're looking for the name that comes from the Greek or the one that comes from the Latin. Or alternatively, you could allow either answer.
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