Which of the following straight lines are both tangent to the circle x2+y2−6x+4y−12=0?A4x+3y+19=0,4x+3y−31=0B4x+3y+19=0,4x+3y+31=0C4x+3y−19=0,4x+3y−31=0D4x+3y−19=0,4x+3y+31=0