Chris Carter’s 3-run home run in the 3rd inning gave the Astros a 3-2 lead. ( Smiley N. Pool / Houston Chronicle ) Time and time again, the Astros left Brett Oberholtzer without backup, stranded when he deserved better. The SOS calls finally went through and the Astros’ most powerful artillery arrived Monday, when the Astros ripped four home runs in a 7-3 win over the A’s — three of them in a span of four batters in the sixth inning.