|Question 15Verbal

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Text
In the periodic table, an element's atomic number indicates how many protons there are in an atom of the element. For example, a calcium atom _____ 20 protons. Professor Raymond Chang explains this concept in more detail in the textbook Chemistry.
Which choice completes the text so that it conforms to the conventions of Standard English?
is having
A
had
B
has had
C
has
D