When we see something with a high correlation coefficient, we know that these two things trend in the same direction (which eliminates D). However, we must remember that correlation does not mean causation, so A and B are also out.
A correlation factor of +0.87 means the two variables: baby weight and computer price, move in the same direction. But it does not say anything about cause and effect.
So the correct statement is C. As the baby gains weight, the computer price tends to increase.
