Consider the following statements with regard to Lissajous pattern on a CRO :
1. It is a stationary pattern on the CRO.
2. It is used for precise measurement of frequency of a voltage signal.
3. The ratio between frequencies of vertical and longitudinal voltage signals should be an integer to have a steady Lissajous pattern.
Which of the above statements is/are correct ?
(a) 1 only (b) 2 only (c) 3 only (d) 1, 2 and 3