请教GWD31-10-Q26&Q33，多谢！

Q26:

On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow, as seen in the rings visible in the cross sections of their trunks.

1. On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow
2. On Earth, among the surest indications of sunspot cycles are, it is believed, the rate of tree growth
3. On Earth, the rate at which trees grow is believed to be among the surest indications of sunspot cycles
4. Among the surest indications on Earth of sunspot cycles, believed to be the tree growth rate
5. Among the surest indications on Earth of sunspot cycles is believed to be the rate at which trees grow

答案选C。我实在是看不太懂这个句子，谁能帮忙解释一下吗？

Q33:

After more than four decades of research and development, a new type of jet engine is being tested that could eventually propel aircraft anywhere in the world within two hours or help boost cargoes into space at significantly lower costs than current methods permit.

A.      tested that could eventually propel aircraft anywhere in the world within two hours or help

B.       tested that could eventually have the capability of propelling aircraft anywhere in the world within two hours or to help

C.       tested, eventually able to propel aircraft anywhere in the world within two hours, or helping

D.      tested, and it eventually could propel aircraft anywhere in the world within two hours or helping

E.       tested, and it could eventually have the capability to propel aircraft anywhere in the world within two hours or help

答案选的E，我选的A。不是capability of吗？E应该是错误的呀

我怎么记得capable of doing/capability to do呢...

谁来确认一下...

顶楼上,希望有人可以帮忙解释一下.

今天在Prep上看到Q26,可是答案选的E,谁知道这道题到底应该选那一个?多谢!