Answer:
Equation (c) 9x - 12y = 24 would cause a consistent-dependent system
Step-by-step explanation:
Given equation 3x − 4y = 8
We have to find the equation from the given option that would cause a consistent-dependent system.
A given system of linear equation 
If a consistent system has an infinite number of solutions, it is dependent . When you graph the equations, both equations represent the same line that is slope of both the equation will be same.
that is possible when
is multiple of
and
is multiple of
and this multiplication factor is same for both.
Thus, for the given equation 3x − 4y = 8
Only equation (c) 9x - 12y = 24 is a multiple of equation 3x − 4y = 8 with same factor of multiplication 3
Also, the slope of two equation is same 
Thus, equation (c) 9x - 12y = 24 would cause a consistent-dependent system