|Which is correct?
In late 2008, Nortel and T-Mobile tested LTE under __________ conditions.
a. every day
Explanation: Every day means each day. Everyday is an adjective that means daily, usual or normal. Everyday conditions are the type of conditions normally encountered. An everyday occurrence is something that occurs every day or something that occurs in the normal course of affairs.
(un)Enlightened English has more about this issue.