Which test should be checked weekly if old stocks of malathion are used by the person handling pesticides?

Correct option is B

Blood cholinesterase activity must be checked weekly for individuals exposed to organophosphate pesticides like malathion. Low levels indicate toxic exposure, as these pesticides inhibit cholinesterase enzymes.
Explanation of other options:
(a) Alanine aminotransferase: Indicates liver function, not pesticide exposure.
(c) Alkaline phosphatase: Related to bone and liver health.
(d) Aspartate aminotransferase: Reflects liver and heart function, not pesticide toxicity.