For this problem we need to know that a linear proportional function occurs when the dependent variable is and the independent variable is also 0. If we analyze the possible options we see this:
A) When x=0 then y= 3. Not satisfy the condition
B) When x=0 then y= 5. Not satisfy the condition
C) When x=0 the y=0 so that represent the answer
D) When x=0 then y=2. Not satisfy the condition
Then the best answer would be C)