Correct Option: A

Photoperiodism is the developmental responses of plants to the relative lengths of light and dark periods. It affects the vegetative growth as well as the time of flowering and fruiting in plants. For example, some annual plants may be made to complete their life cycle twice in a year, while others can be made to take on characteristics of everlasting flowering species and continue to produce flowers and fruits on an indefinite period, while in yet other species the plant may continue vegetative development indefinitely without flowering.