C meets the trading requirement if C is—
a trading company which is not a member of a group, or
the principal company of a trading group.
"Trading company" means a company carrying on trading activities whose activities do not include to a substantial extent activities other than trading activities.
"Trading group" means a group—
one or more of whose members carry on trading group activities, and
the activities of whose members, taken together, do not include to a substantial extent activities other than trading group activities.
In this section—
"trading activities" means activities carried on by the company in the course of, or for the purposes of, a trade being carried on by it;
"trading group activities" means activities carried on by a member of the group in the course of, or for the purposes of, a trade being carried on by any member of the group.
For the purposes of determining whether C is a trading company or the principal company of a trading group—
the activities of the members of a group are to be treated as one business (with the result that activities are disregarded to the extent that they are intra-group activities), and
a business carried on by a company in partnership with one or more other persons is to be treated as not being a trading activity or a trading group activity.