The correct answer is: C. have become
Washing machines have become popular in India in the last ten years or so. This is because the cost of washing machines has decreased, while the income of people has increased. Additionally, there is now a greater awareness of the benefits of using washing machines, such as saving time and energy.
Option A, “became,” is incorrect because it implies that washing machines suddenly became popular in India at a specific point in time. This is not the case, as the popularity of washing machines has gradually increased over the past decade.
Option B, “are become,” is incorrect because it is grammatically incorrect. The correct verb tense to use in this sentence is “have become.”
Option D, “are becoming,” is incorrect because it implies that the popularity of washing machines is still increasing. While it is true that the popularity of washing machines is still increasing, the rate of increase is slowing down.