Q35 to Q37:

(This passage was excerpted from material

published in 1996.)

      When a large body strikes a planet

       or moon, material is ejected, thereby

       creating a hole in the planet and a local

Line       deficit of mass.  This deficit shows up

  (5)      as a gravity anomaly:  the removal of

the material that has been ejected to

make the hole results in an area of

slightly lower gravity than surrounding

areas.  One would therefore expect that

 (10)      all of the large multi-ring impact basins

on the surface of Earth’s Moon would

show such negative gravity anomalies,

since they are, essentially, large holes

in the lunar surface.  Yet data collected

 (15)      in 1994 by the Clementine spacecraft

show that many of these lunar basins

have no anomalously low gravity and

some even have anomalously high

gravity.  Scientists speculate that early

 (20)      in lunar history, when large impactors

       struck the Moon’s surface, causing

       millions of cubic kilometers of crustal

debris to be ejected, denser material

from the Moon’s mantle rose up

 (25)      beneath the impactors almost imme-

diately, compensating for the ejected

material and thus leaving no low gravity

anomaly in the resulting basin.  Later,

however, as the Moon grew cooler

 (30)      and less elastic, rebound from large

impactors would have been only partial

and incomplete.  Thus today such

       gravitational compensation probably

would not occur:  the outer layer of

the Moon is too cold and stiff.

from the Moon’s mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no low gravity anomaly in the resulting basin.

這句話在解釋會何沒有第九行說的那個現象

這裡要注意這個"early"

然後在第32行

Thus today such

gravitational compensation probably

would not occur:

所以在"today"不會有"compensatiion"

因此如果會有negative gravity  anomalies 就是發生在現在了

还是不是很理解

E为啥不对呢?

A可以理解了

但B呢？basin就是由于撞击产生碎片后形成的，如果月球的地幔物质可补偿那个basin的话，basin就不存在了。