【单选题】

Male lions are rather reserved about expending their energy in hunting. More than three-quarters of kills are made by lionesses. Setting off (1) dusk on a hunt, the lionesses are in (2) , tensely scanning ahead, the young lions fall playfully behind, and the (3) bring up the rear, walking slowly, their massive (4) nodding with each step as if they (5) with the whole matter.But (6) may have survival value. (7) lionesses busy hunting, the males (8) as guards for the young, (9) them particularly from hyenas (土狼).

Hunting lionesses have learnt to take advantage of their (10) .Darkness (11) them with cover, and at dusk they (12) wait near animals they want to kill (13) their outlines blend into the surroundings. Small prey (猎物) present lions with no (14) . They are simply grabbed with the paws.A、 (15) technique is used with (16) animals, such as wildebeest ( 角马). Usually a lioness pulls her prey down (17) running up behind (18) , and then seizes it (19) the throat. Or she may place her mouth over the muzzle (动物之鼻口) of a downed animal, (20) it.
A．at
B．on
C．in
D．under