Analyse the given data and answer the questions given below:
A student measures the time taken by a pendulum to complete \(10\ oscillations\) in three trials.
| Trial | Time for \(10\ oscillations\) |
| 1 | \(20\) |
| 2 | \(21\) |
| 3 | \(20\) |
1. In Trial \(2\), the pendulum takes \(21\ s\) to complete \(10\ oscillations\). What is its time period?
2. Which of the following correctly gives the time periods for Trials \(1\), \(2\) and \(3\) respectively?
3. What is the most appropriate conclusion the student can draw from the three observations?
4. Why is it useful for the student to perform the pendulum experiment in several trials?