sat 语法题求助,

sat 语法题求助,
1.Despite research( on the diagnosis of) heart disease and the use of (increasingly) sophisticated technology (in its treatment),the condition of coronary arteries (is) still difficult to assess precisely.可是我觉得its 指代不清啊,之前有diagnosis,disease,use.如果把句子变简洁的话,就应该是its 指代diagnosis,可是根据句意应该指代disease啊,难道修剪句子的方法不灵了,its到底怎么判断啊!
2.06年5月的真题
（Having millions of gallons of freshwater ) underground ,Florida environmentalists work to educate the public on the dangers of ground pollution.
A.
B.Because millions of gallons of freshwater are
觉得A 用动词ing放句首表示原因没错啊,况且A比B短,答案为什么就选B