Plant growth caused by external stimulus is
a. tropism
b. homeostasis
c. gibberllin
d. hormone

The correct answer for the blank is-

A. tropism.

Tropism is a biological process that indicates growth of a plant in a particular direction in response to any external stimuli (any change in the environment that induces a specific response in a biological system).

For example - Phototropism in plants is a type of tropism process in which plants tend to grow towards the direction of sunlight.

Thus, option A) is the right answer.

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)

it would be heredity