OG11 103 104 106 关于2个并列的成分是否要用逗号隔开的问题

A newly developed jumbo rocket, which is
expected to carry the United
  States into its next phase of space
exploration, will be able to deliver a heavier load of instruments into orbit
than the space shuttle can, and at a lower cost. 

and at a lower cost 被用逗号给隔开了。它应该是和第一个clause will be able to deliver...并列的 补充完整就是 

 will be able to deliver a heavier load of instruments into orbit than the space shuttle can , and  (will be able to deliver a heavier load of instruments into orbit) at a lower cost (than the space shuttle can). 

OG104 D选项 

Nuclear fusion is the force that powers the
Sun, the stars, and hydrogen bombs, and merges the nuclei of atoms but does not
split them apart, as is done in nudear reactors      

ETS的comments是” Illogical and awkward
construction attempts to make merges the second verb of the restrictive clause
parallel to powers and does not split； punctuation makes clear this separate action cannot be
the case;”

关于这句“punctuation makes clear this separate action cannot be the case”我不是很理解，它是指第二个并列的成分之前不能用逗号隔开，还是说 原句 “Nuclear fusion is the force that powers the
Sun, the stars, and hydrogen bombs, merging the nuclei of atoms and not
splitting them apart, as in nuclear reactors.”中 merging...这个句子被用逗号隔开，说明对整个句子不重要的一个修饰成分，所以merge不能作为和第一个verb power同等重要的第二个平行的verb? 

OG106 C选项

Among the objects found in the excavated temple were
small terra-cotta effigies left by supplicants who were either asking the
goddess Bona Dea's aid in healing physical and mental ills, and thanking her for helping

Who
were either asking…, and thanking…

According to ETS, No comma should be used before
and..

到底2个并列的成分可不可以用逗号隔开，OG自己都自相矛盾了么！！！ 

它的正确选项A：