The argument looks something like the following
Something occurs = with decreased production prices have increased
Analysts' explanation = very little of the rice is sold on the world market
The analysts' explanation is the conclusion of the argument. To weaken the analysts' explanation in this question we'll need to find a weakness in the argument's reasoning. Sometimes, other questions similar in structure will undermine the explanation by providing an equally likely alternative explanation. None of the answers do that here, so we need to look at the reasoning within the argument for a possible weakness found in an answer choice.
(A) is irrelevant. What rice-importing countries do after the price rises doesn't explain why the price had risen in the first place.
(B) supports the analysts' explanation by making it so that people who would have gotten their rice from the government now must find it on the free-market. Thereby further increasing demand.
(C) undermines the analysts' explanation by making it so that when production falls governments release more rice into the world market, thus, increasing supply and making it less likely that price increases were the result of shortages.
(D) supports the analysts' explanation by saying that in times of decreased production, local governments purchase rice on the world market, thus reducing supply even further.
(E) supports the analysts' explanation by making it so that rice-importing countries cannot compensate with alternative crops when rice production is low.