There are four questions below，

As of the late 1980's. neither theorists nor large- scale computer climate models could accurately predict whether cloud systems would help or hurt a warming globe. Some studies suggested that a four percent increase in stratocumulus clouds over the ocean could compensate for a doubling in atmospheric carbon dioxide, preventing a potentially disastrous planetwide temp- erature increase. On the other hand, an increase in cirrus clouds could increase global warming.

That clouds represented the weakest element in cli- mate models was illustrated by a study of fourteen such models. Comparing climate forecasts for a world with double the current amount of carbon dioxide, researchers found that the models agreed quite well if clouds were not included. But when clouds were incorporated, a wide range of forecasts was produced. With such discrepancies plaguing the models, scientists could not easily predict how quickly the world's climate would change, nor could they tell which regions would face dustier droughts or deadlier monsoons.

The author of the passage is primarily concerned with

It can be inferred that one reason the fourteen models described in the passage failed to agree was that

It can be inferred that the primary purpose of the models included in the study discussed in the second paragraph of the passage was to

The information in the passage suggests that sci- entists would have to answer which of the following questions in order to predict the effect of clouds on the warming of the globe?