Hi,

when you leave one company and join another company at that time new company where you have joined also gives you one form to filling up. in that form you are supose to write old company details and about your past PF account number so you need not to worry. without actual joining your PF cannot be transfered. coz it required both parties approvel so if one company gives transfer order of your PF account to PF dept but if another company is not giving the details regarding new joined candidate and request of PF account transfer of that candidate, your PF account can't be transfer. so you may join company C.

Regards
suvarna