Silk, although it is considered a delicate fabric, is in fact very strong, but it is adversely affected by sunlight.

【正确答案】 C

【答案解析】解析：题干：虽然人们认为蚕丝是一种脆弱的织物，事实上它却非常坚固，但是阳光会对它产生不利影响。delicate易碎的，脆弱的。A选项：软的。B选项：完全的。C选项：易碎的，脆的。D选项：精制的。