|Question 16Verbal

Source Texts

Text
In the periodic table, an element's atomic number indicates the number of protons in an atom of that element. For example, there are 25 protons in a manganese atom. Raymond Chang's textbook General Chemistry: The Essential Concepts _____ this concept in detail.
Which choice completes the text so that it conforms to the conventions of standard English?
discussing
A
discusses
B
to discuss
C
having discussed
D