Final answer:
The slope of the second line must be 4/3 if it is parallel to the first line.
Step-by-step explanation:
The slope of the second line must be 4/3 if it is parallel to the first line.
When two lines are parallel, they have the same slope. Since the slope of the first line is given as 4/3, the slope of the second line must also be 4/3.
Therefore, the correct answer is A. 4/3.