Scientists have: (select all that apply.) a. observed amino acids forming spontaneously b. demonstrated how amino acids can form from the environment c. confirmed that the ultimate source of amino acids and proteins is from plants d. not yet determined the source of amino acids

Scientists have: (Select all that apply.) 
a. observed amino acids forming spontaneously 
b. demonstrated how amino acids can form from the environment 
c. confirmed that the ultimate source of amino acids and proteins is from plants
d. not yet determined the source of amino acids

The correct answers are:

Demonstrated how amino acids can form from the environment
Confirmed that the ultimate source of amino acids and proteins is from plants