If the phase difference between two signals is 180°, then the Lissajous pattern will be _________.
1
an ellipse with major axis in 2nd and 3rd quadrants
2
a straight line with major axis in 2nd and 4th quadrants
3
an ellipse with major axis in 1st and 4th quadrants
4
a circle with major axis in 1st and 4th quadrants