After a three-week strike that brought the Paris public transit system to its knees, four of five French transit unions agreed to accept a pay offer. But the fifth union, the Communist-led CGT, refused to reconsider its rejection of the offer and held out for a pay rise three times as large as the $50 monthly increase offered by the regional transport network. Prior to the strike, workers were earning a base monthly wage of $1,100. Spokesmen for the four unions that accepted the offer said they will urge their members to return to work on buses, subways and suburban trains. But transport officials have said that CGT union participation is essential in any agreement, and it was unclear how the Paris system would be affected if the CGT walkout continued.