Elephants are one of the most intriguing and wonderful animals on earth.　The elephant is the largest mammal, ___(21)___ up to 5 meters in height and 5,000 kgs in weight.　This extraordinary creature is unusual even before birth.　The mother elephant carries her unborn baby for the ___(22)___ of twenty-two months, which is the longest period of time among all mammals.　A newborn baby elephant can be one meter tall and weigh 135 kilograms.　The elephant family is ___(23)___.　Right after the baby is born, some adult female relatives will ___(24)___ to take care of the newborn until it reaches adulthood.　In the elephant herd, the older and the stronger tend to protect the younger and the weaker. Believe it or not, elephants are ___(25)___ vegetarians.　Grass, small branches, and bark from trees are among their favorite foods.
【題組】21.
(A) that is measured　
(B) measuring　
(C) which measure　
(D) to be measuring