Please read the following excerpt from an article:

" As President Barack Obama prepares to depart Thursday for his first Asia trip, Chinese premier Wen Jiabao is urging the U.S. to keep its deficit to an "appropriate size," a clear message to the leader of the world's largest debtor nation from its largest creditor.

China is the largest holder of U.S. government debt and has invested an estimated 70% of its more than $2 trillion stockpile of foreign-exchange reserves (the world's largest) in dollar assets, Reuters reports. Further dollar weakness, brought on by enormous U.S. deficit spending and near-zero interest rates, would erode the value of China's huge U.S. holdings. "Most importantly, we hope the United States will keep an appropriate size to its deficit so that there will be basic stability in the exchange rate, and that is conducive to stability and the recovery of the global economy," Wen Jiabao said over the weekend at a news conference in Egypt.

In contrast, the best strategy for the U.S. may be an inflationary stance. We need stimulus spending to jump start our economy and reduce the real value of our record budget deficit of $1.42 trillion in the fiscal year that ended Sept. 30. An improved U.S. economy also would mean more Americans buying up Chinese-made goods"

Please comment on the following questions:

Why is China concerned about the value of US dollar? What can they do to decrease their exposure to fluctuations in the value of US dollar? Is decreasing exposure to US dollar an easy task for China? Why?