Paul Ehrlich argued that overpopulation was responsible for environmental problems.
arrowRight
The first national Earth Day marked the largest demonstration in American history.
arrowRight
President Eisenhower asked the Public Health Service to study ways to control air pollution.
arrowRight
The Santa Barbara oil spill led to reforms in the energy industry.

the correct answer is option b

behavioral response need communication and thus co-ordination at several levels such as interaction among cells, organ system and the entire organism.

behavioral response produces both internal and environmental stimulus.

answer: b

coz red blood cells marrow and circulates the body for 120 days.

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers