Which one of the following is correct for blooming of short day plants?

The plants that flower, when day length is less than a certain critical length, are called short-day plants. For example, Xanthium flower, Tobacco and Strawberry.

They cannot flower under short nights or if a pulse of artificial light is shone on the plant for several minutes during the night; they require a continuous period of darkness before floral development can begin. Natural nighttime light, such as moonlight or lightning, is not of sufficient brightness or duration to interrupt flowering.

So, the correct option is B.