Oil majors Exxon (XOM), Royal Dutch Shell (RDS-A) and ConocoPhillips (COP) all reported lower results from a year ago on Thursday, weighed down by the plunge in oil prices. Exxon posted a 46% drop in first-quarter profit, though earnings and revenue still beat analysts' expectations. Refining and marketing earnings were a pocket of strength, more than doubling to about $1.6 billion. Refining and marketing also aided Shell's results, rising to $2.6 billion from about $1.6 billion a year ago. However, Shell reported earnings that fell by 56% from a year ago, with its adjusted profit falling to $3.2 billion from $7.3 billion last year. ConocoPhillips reported a narrower-than-expected first-quarter loss of $0.18 a share, compared to analysts' estimates for a loss of $0.19 a share.