What withholding status must the employer use for his first paycheck?

An employee is married with one child. His beginning salary is $1,000 semimonthly. because of an unexpected business trip, the employee fails to submit a 2020 form W4 by his first payday.

What withholding status must the employer use for his first paycheck?
A . single/married filing separately, no entries in steps 2,3,4
B . married filing jointly, no entries in steps 2,3,4
C . single/married filing separately, entry in step 3 for one dependent
D . married filing jointly, entry in step 3 for one dependent

Answer: A