Statement: The cotton crop continues to be poor even after the introduction of improved variety of cotton seeds.
Assumptions:
I. The yield of cotton was expected to increase after introduction of improved variety of seeds.
II. The yield of cotton was adequate before the introduction of new variety of seeds.

The statement talks about the poor yield of cotton even after the introduction of a new variety of seeds. 

We shall try negating the assumption and see if it invalidates the main statement as well for it to be a valid conclusion.

1. Had the yield not been expected to improve after the introduction of a new variety of seeds, the main statement would not be mentioned the same and seeds wouldn't have been introduced in the first place. Hence, a valid assumption.

2. Had the yield been adequate before the new seeds, they would not have been introduced in the first place. Hence, an invalid assumption.