Heterosis is:

The correct option is B Hybrid vigor
Heterosis or hybrid vigor is an outbreeding enhancement method which improves or increases the function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. The progeny of crosses between different varieties of a plant species usually exhibit greater biomass and fertility than either parent. This phenomenon is called heterosis or hybrid vigor.