The first term of an A.P. is p and its common difference is q. The 10th term of the A.P. is :

1. p − 9q

2. p + 10q

3. p − 10q

4. p + 9q

For what value of k will 2k + 1, 3k + 3, and 5k − 1 be three consecutive terms of an A.P.?

1. 1

2. 2

3. 4

4. 6

If the sum of first n terms of an A.P. is S_n = 5n² + 3n, then its common difference is:

1. 8

2. 10

3. 18

4. 26