Which of the following are possible causes of material price variance?
1. Change in market price.
2. Use of poor quality of material.
3. Inefficient buying.
4. Untimely buying.
5. Paying overtime for urgent work.
6. Use of substitute material of different prices.
Select the correct answer:

A. 1, 3, 4 and 6

B. 2, 3, 5 and 6

C. 3, 4, 5 and 6

D. 1, 3, 5 and 6

Answer: Option A