In an ellipse, the variable is always matched with the variable whose axis parallels the direction.

a. horizontal
b. narrower
c. vertical
d. wider

B. Narrower.

Step-by-step explanation:

We have been given an incomplete statement. We are supposed to complete the given statement.

Statement: In an ellipse, the variable is always matched with the variable whose axis parallels the __________ direction.

We know that standard equation of an ellipse with a major axis parallel to x-axis is in form:

We know that standard equation of an ellipse with a major axis parallel to y-axis is in form:

The variable is matched with the variable, whose axis is parallel to wider direction and variable is matched with the variable, whose axis is parallel to narrower direction.

Therefore, option B is the correct choice.