Many Asian economies saw factory activity slow in March, business surveys showed on Wednesday, a sign surging fuel costs and heightening global uncertainty from the Iran war were taking a toll on the region. The findings highlight the challenge policymakers face in a region that buys about 80% of the oil that is shipped through the Strait of Hormuz, making many countries vulnerable to the hit from the energy shock caused by the war. China's manufacturing sector expanded in March for a fourth straight month but saw inflationary pressures and supply chain strains intensify, a private survey showed.