Chromosome 21 is -

Ans. is 'c' i.e., Acrocentrico Each chromosome has two armsi) p arm (the shorter of two)ii) q arm (longer one)o Depending on the position of there junction (centromere) they can be classified into :1. Metacentric# The centromere is in the middle so that the two arms of chromosomes are almost equal.# These chromosomes are : chromosomes 1,2, 3 and X-chromosome.2. Submetacentric# p arm is short and q arm is long.# These chromosomes are : 4, 5, 6, 7, 8 and 9.3. Acrocentric# p (short) arm is so short that it is hard to observe, but still present.# There are six acrocentric chromosomes : 13,14,15,21,22 and Y chromosomes.