|Question 20Verbal

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The Roman poet Lucan's Pharsalia, an epic poem about Julius Caesar, is an extant work: it can still be read. By contrast, lost works like Lucan's poem praising Emperor Nero, Laudes Neronis—no copy of which exists—______ known to antiquarians only through references in extant works.
Which choice completes the text so that it conforms to the conventions of Standard English?
have become
A
is becoming
B
has become
C
becomes
D