单选题
In theory, millions of people suffering devastating diseases may one day be helped or even cured with treatments derived from human embryonic stem cells, but human embryos must be destroyed to obtain these stem cells. So research involving them is ______ in controversy, with each side arguing passionately for the rights of the sick or the rights of the unborn.
【正确答案】
D
【答案解析】[解析] D选项：mired意为“深陷”，如：The United States became mired in wars in Iraq．(美国深陷伊拉克战争泥潭。)句意：相关的研究陷入争论之中。或为患者的权利，或为未出生的婴儿的权利，各方进行着激烈的辩论。故选D。
其他三项：refuted驳斥；modified修改；marred毁坏。