'The number of pairs of these in mammals varies from 9 in whales to 24 in sloths; humans normally have 12'
ribs
BONE UP FOR THE TEST: The number of pairs of these in mammals varies from 9 in whales to 24 in sloths; humans normally have 12
The number of pairs of these in mammals varies from 9 in whales to 24 in sloths; humans normally have 12
The number of pairs of these in mammals varies from 9 in whales to 24 in sloths; humans normally have 12
BONE UP FOR THE TEST
ribs
BONE UP FOR THE TEST