When two unrelated individuals or lines are crossed, the performance of $F_1$ hybrid is often superior to…
When two unrelated individuals or lines are crossed, the performance of $F_1$ hybrid is often superior to both its parents. This phenomenon is called
transformation
splicing
metamorphosis
heterosis
Solution
The superiority of hybrids over either of the parents (dominante or recessive is called hybrid vigour (G. Shull). Heterosis is equivalent of hybrids vigour.