A biologist was interested in determining whether sunflower seedlings treated with an extract fromVinca minorroots resulted in a lower average height of sunflower seedlings than the standard height of 15.7 cm. The biologist treated a random sample of 33 seedlings with the extract and subsequently obtained a mean of 13.664 cm and a standard deviation of 2.544 cm for the heights of the plants.

What are the researcher's hypotheses?

Select one:

a. H_o: = 13.664 H_a: > 13.664 b. H_o: = 15.7 H_a: > 15.7 c. H_o: = 15.7 H_a: < 15.7 d. H_o: = 13.664 H_a: < 13.664 e. H_o: = 15.7 H_a: 15.7