Doctors sometimes have difficulty diagnosing viral pneumonia because the early symptoms of this potentially deadly illness are often quite similar to the common cold.
a) are often quite similar to the common cold
b) often resemble that of the common cold
c) are often quite similar to those of the common cold
d) are often quite similar to the common cold's symptoms
e) quite often are, like the common cold, similar
A is wrong compares symptoms to common cold
B uses resemble and changes meanings
D uses possessive form.
E is awkward.
C is better compared to D as it is concise.