It is theoretically possible that bacteria developed on Venus early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So, even if bacteria did arrive on Earth from Venus, they must have died out.
The argument is most vulnerable to which of the following criticisms?
It fails to establish whether bacteria actually developed on Venus
It fails to consider whether all bacteria now on Earth could have arisen from transported Venusian bacteria
It fails to consider whether there were means other than meteorites by which Venusian bacteria could have been carried to Earth