China's services activity expanded at the fastest pace in three months in May, helped by stronger growth in new business and a rebound in overseas demand, though rising cost pressures weighed on firms, a private-sector survey showed on Wednesday. The RatingDog China General Services Purchasing Managers' Index, compiled by S&P Global, rose to 54.4 in May from 52.6 in April, staying above the 50-mark that separates expansion from contraction.