It is theoretically possible that bacteria developed on Mars 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 Mars, they must have died out.

The argument is most vulnerable to which of the following criticisms?

1. It fails to establish whether bacteria actually developed on Mars.

2. It fails to establish how likely it is that Martian bacteria were transported to Earth.

3. It fails to consider whether there were means other than meteorites by which Martian bacteria could have been carried to Earth.

4. It fails to consider whether all bacteria now on Earth could have arisen from transported Martian bacteria.

5. It fails to consider whether there could have been strains of bacteria that originated on Earth and later died out.

Answer: D

选是选对了，通过是否与题有关无关；但是不知道其中意思，请NN拆解。

细菌最早是从火星发源并被流星带入地球。然而，从不同星球来的细菌的后代

应该在蛋白机构（能够持续很长时间）上有很大的不同。但并没有两种细菌的

后代有很大的不同以至于是从两个不同的星球来的。因此，即使细菌确实是从

火星上来的，那么他们也都死光了。

D. 它没有考虑地球上的所有细菌都是从火星上来的这中情况。

因此，这种结论是不对的。