Milankovitch proposed in the early twentieth century that the ice ages

Really... a tough one.. I was completely blown ......

here are my answers with explanations:

1. In the passage, the author is primarily interested in

Ans : (D) presenting a theory and describing a new method to test that theory
The author mentions the theory presented by Milankovitch and states that for some time this theory was untestable. It is also mentioned in next para that a recent discovery helps in testing the validity of the theory mentioned by Milankovitch.

2. The author of the passage would be most likely to agree with which of the following statements about the Milankovitch theory?

Ans : Answering this question consumed most of my time while solving this passage. I was confused between options A and D. My pick for this is
(D) It is one plausible explanation, though not the only one, for the ice ages.

As it has already been mentioned in the passage that Milankovitch's theory can be tested if chronology of ice ages is known. Now measuring the relative amount of land ice that existed during various times in the earth's past is helpful in determining the chronology of ice ages and the amount of land ice can be predicted using the findings of the recent discovery. So the answer B, C and E are out. Now between A and D we need to confirm if the theory is the only way to find the volume of land ice. The author mentions in last passage that there are some other factors as well such as volcanic particulates or variations in the amount of sunlight received by the earth which could potentially have affected the climate. The only reason for which the author chose the Milankovitch's theory is that it is testable. There are other factors but they are not considered just because of the lack of information about them.

3. Itcan be inferred from the passage that the isotope record taken from ocean sediments would be less usefulto researchers if which of the following were true?
Ans : (B) It had far more gaps in its sequence than the record taken from rocks on land.
It is clearly mentioned in lines 37-39 that records taken from ocean sediments are advantageous because they are more continuous in nature that those taken from rocks on land.

4. According to the passage, which of the following is true of the ratios of oxygen isotopes in ocean sediments?
Ans : (c) They can be used to deduce the relative volume of land ice that was present when the sediment was laid down.
It is clearly mentioned in lines 12 to 14 that relative land-ice volume for a given period can be deduced from the ratio of two oxygen isotopes,16 and 18, found in ocean sediments.

5. It can be inferred from the passage that precipitation formed from evaporated ocean water has
Ans : (B) less oxygen 18 than does ocean water
It is mentioned in lines 20 to 24 that when water evaporates the heavier isotope remains in ocean water. This clearly causes the concentration of oxygen 18 to decrease in evaporated water. So precipitation formed from evaporated water will have less oxygen 18 than that in oceanic precipitations.

6. Itcan be inferred from the passage that calcium carbonate shells
Ans : (E) reflect the isotopic composition of the water at the time the shells were formed
From lines 24 to 29 it can be inferred that calcium carbonate shells were constructed using the oceanic water at the time of their composition. So the oxygen isotope's concentration found in their analysis will show the concentration of isotopes in oceanic water.

Carcass, It has taken a lot of time in formatting the question in my post but if some errors are still persisting, I am worried about them. Request you to review the answers and explanations. Its 3:40 am here...So i m gonna sleep with hope to get reply from you when i wake up .... It was really tough question. :done

Pressing +1 Kudos is the best way to say Thanks!