Assertion (A): Insect resistant transgenic cotton has been produced by inserting Bt gene. Reason (R): The Bt gene is derived from a bacterium.

The correct answer is A because both statements are factually accurate and the reason directly explains the assertion. Assertion A is true because scientists have developed genetically modified cotton, known as Bt cotton, which is resistant to pests like the bollworm. This resistance is achieved by inserting a specific gene called the Bt gene into the cotton plant DNA. Reason R is true because the Bt gene is derived from Bacillus thuringiensis, which is a common soil bacterium. The reason is the correct explanation for the assertion because the prefix Bt in Bt cotton specifically refers to the bacterium from which the insecticidal gene was taken. The insertion of this specific bacterial gene is what provides the cotton plant with the transgenic trait of insect resistance.