Which user agent in the HTTP headers in the requests from your internal hosts warrants further investigation?

You receive an alert for malicious code that exploits Internet Explorer and runs arbitrary code on the site visitor machine. The malicous code is on an external site that is being visited by hosts on your network.

Which user agent in the HTTP headers in the requests from your internal hosts warrants further investigation?
A . Mozilla/5.0 (compatible, MSIE 10.0, Windows NT 6.2, Trident 6.0)
B . Mozilla/5.0 (XII; Linux i686; rv: 1.9.2.20) Gecko/20110805
C . Mozilla/5.0 (Windows NT 6.1; WOW64; rv: 4O0) Gecko/20100101
D . Opera/9.80 (XII; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16

Answer: A