<s>[INST] context: In urban areas, Malaria is mainly transmitted by Anopheles stephensi.
Recommended measures for Urban Malaria contro l: Breeds in man-made water containers in domestic / peridomestic situations such as tanks, wells, cisterns, which are of permanent nature and hence can malaria transmission throughout the year.
Measures for Urban Malaria Control:

Lids of overhead tanks must be checked and maintained monthly basis; any leakage be repaired immediately (most effective).
Cover-up of underground and open tanks.
Open tanks used for animals be dead dried once in week Never to throw any containers in open capable of holding water.
Construction sites: Building bye-laws be implemented to prevent fault in designs, water flow on roof, gully traps open tanks for curing be treated with larvicides on weekly basis.
Unused wells either be closed or treated with larvicides Ornamental tanks, fountains be checked periodically and larvivorous fish be introduced
Public health engineers be involved for proper drainage, building designs, periodic flushing of water logged areas and drainage. [/INST] question: Most efficient anti­larval measure to prevent urban malaria is | options: A: Clean drainage and sewerage systems B: Cover overhead tanks properly C: Filling cesspools and ditches D: Cover pits | answer: B </s>