After upgrading a fiber link from 1Gbps, a network technician ran a speed test of the link. The test shows the
link is not operating at full speed and connectivity is intermittent. The two buildings are 1.476ft (450m) apart and
are connected using CM4 fiber and 10G SR SFPs. The fiber runs through the electrical and boiler rooms of
each building. Which of the following is the MOST likely reason for the connectivity issue?

A.
The wrong SFPs are being used

B.
There is interference from the electrical room.

C.
CM1 fiber should be used instead

D.
There is heat from the boiler room

Explanation:
http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/data_sheet_c78-
455693.html