Select the most appropriate option to substitute the underlined segment in the given sentence. If there is no need to substitute it, select No substitution required.
Normally bacteria are present in our mouth but it is not harmful to us. (a) No substitution reqired (b) so they are not (c) and it is not (d) but they are not

Options

A. No substitution reqired
B. so they are not
C. and it is not
D. but they are not

Answer

D