Which of the following statements about infectious diseases is true?
a. infectious diseases are the leading cause of death in the united states.
b. infectious diseases are caused by pathogens.
c. most infectious diseases can be cured by antibiotics.
d. infectious diseases cannot be transmitted from animals to humans.

B. Infectious diseases are caused by pathogens.

Explanation:

Any disease-causing organism is called a pathogen. The infectious diseases are the ones that are caused by pathogens. Some of the pathogens that cause these diseases are bacteria, fungi, viruses, protozoans, and prions. These diseases are transmitted from the affected individual to the healthy one by one or other means. For example, rabies is an infectious disease that is acquired through contact with a rabid animal. Only bacterial diseases can be cured by antibiotics. Some examples of infectious diseases are malaria, dengue, hepatitis, tuberculosis, etc.

i'd say that the moon rock is about 2.2 billion years old.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.