Chemical messengers that influence the activity of another cell are chemical messengers. On the other hand, chemical messengers that influence the activity of the same cell that releases them are chemical messengers.

answer; ///i believe its: ///(embolus);

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