Find the points on the curve y=3x4+2x3-1 at which the tangents is parallel to the x-axis.

• A. (0,1) and ((- frac{1}{2},- frac{15}{16}) )
• B. (0,-1) and ((- frac{1}{2},- frac{15}{16}) )
• C. (0,-1) and (( frac{1}{2},- frac{15}{16}) )
• D. (0,1) and (( frac{1}{2}, frac{15}{16}) )