Two students were testing the amount of fertilizer that would best promote the growth of strawberries in a garden. Which of the following could be an unavoidable source of experimental error?

A. Variation in the strawberry plants

B. The cost of watering the plants

C. Fertilization during the study

D. Length of the study

The correct answer is option (A) Variation in the strawberry plants.

When the effect of fertilizer on the growth of two strawberry plants is tested, unavoidable source of experimental error is the variation in the strawberry plants. Variation refers to the deviation or differences from the normal plant which can be due to genetic variation. It is due to change in the DNA sequence. If any one of the two plants being tested show variation, the rate of metabolism differs and changes the growth pattern of the plant. The rate of absorption of water and nutrients is effected which brings change in the growth of the plant and causes an error in the experiment and the result.