The number and structure of can to determine evolutionary relationships between species.
a. chromosomes
c. communities
b. populations
d. adenosines

The right answer for blank is-

a. chromosomes.

Explanation:

Chromosomes are the thread like structures, composed of DNA (deoxyribonucleic acid) and possess unit of heredity on them, known as genes ( a segment of DNA that codes for a particular protein).

Genes are transferred from parents to the next generation and thus the genetic information (in the form of sequence of DNA) is transferred from parents to their offspring.

Organisms belonging to same species have same number and structure of chromosomes (such as human beings have 23 pairs of chromosomes with similar structures in all).

Thus, the number and structure of chromosomes helps to determine evolutionary relationships between species.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.