A Gardener in Canada Wants to Surprise His Mother on Her

A gardener in Canada wants to surprise his mother on her birthday and make her favourite hibiscus bush flower in May instead of at the end of June. The bush is growing in the greenhouse. Which of the following might make the hibiscus bush flower early?

A) grafting leaves of a hibiscus that was exposed to long nights
B) grafting leaves of a hibiscus that was exposed to short nights
C) exposing flower buds of the hibiscus bush to long nights
D) exposing flower buds of the hibiscus bush to short nights