12. Tuberculosis (TB), which was once almost
eradicated, is becoming more common, even
in developed countries, because
a. new varieties of the tuberculosis pathogen
have evolved in rodents.
b. livestock are given antibiotics.
c. the pathogen that causes TB breeds in pol-
luted water.
d. some populations of the pathogen that
causes TB are resistant to the antibiotics.

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

answer; civil inattention;