The correct answer is B. Decrease.
In decreasing-term insurance, the premiums paid decrease over time. This is because the amount of insurance coverage decreases over time, as the insured person gets older and the risk of death decreases. The premiums are designed to be level over the term of the policy, so as the coverage decreases, the premiums also decrease.
Option A is incorrect because the premiums paid in decreasing-term insurance decrease over time, not increase.
Option C is incorrect because the premiums paid in decreasing-term insurance decrease over time, not remain constant.
Option D is incorrect because the premiums paid in decreasing-term insurance are not returned, they are simply paid to the insurance company over the term of the policy.