Assertion: Emasculation and bagging are the crucial steps in artificial hybridisation.
Reason: It ensures that the flower is pollinated by pollen grains obtained from desirable varieties only.

The correct option is A Assertion and reason are true, and the reason is the correct explanation of the assertion
Artificial hybridisation is the process by which the desired pollen grains are used for pollination and fertilisation. It includes the following steps.

They are as follows :

Selection of parents with desired characters
↓
Selfing of the selected parents to obtain pure lines
↓
Emasculation (Removal of anthers) is done to prevent self-pollination if the plant considered as female parent produces bisexual flowers
↓
Bagging of the emasculated flowers to prevent contamination by the unwanted pollen grains
↓
Tagging of the emasculated flowers by writing every step with date and time
↓
Artificial pollination of the emasculated and bagged flowers with pollen from the desired plant
↓
Rebagging of pollinated flowers and allowing the development of fruits

Artificial hybridisation is performed for achieving desired characters in the offspring. Out of all the steps, emasculation and bagging ensure that the flowers are pollinated by the desired pollen grains. So the assertion and reason are correct and reason is the correct explanation for assertion.

Figure: Emasculation

Figure: Bagging