下列程序哪个是画一个三角形？（）
turtle.forward(100)turtle.left(120)turtle.forward(100)turtle.right(60)turtle.backward(100)
turtle.forward(100)turtle.left(60)turtle.forward(100)turtle.right(60)turtle.backward(100)
turtle.forward(100)turtle.left(120)turtle.forward(100)turtle.right(60)turtle.forward(100)
turtle.forward(100)turtle.left(120)turtle.forward(100)turtle.right(120)turtle.forward(100)