请教prep一题结构

jason1985716

While they remove carbon dioxide from the air, conserve soil and water, and house thousands
of species, forests also supply potentially valuable pharmaceuticals, and, as sources of building
material and firewood, that provide employment for millions worldwide.

(A) pharmaceuticals, and, as sources of building material and firewood, that provide
(B) pharmaceuticals, and sources of building material and firewood, are providers of
(C) pharmaceuticals and, as sources of building material and firewood that are providing
(D) pharmaceuticals and sources of building material and firewood, for providing
(E) pharmaceuticals and, as sources of building material and firewood, provide 

我想请问正确选项E中，"as sources of building material and firewood"应该是插入语吧，它的意思应该是指 forests吧？

aeoluseros

是的，修饰的是provide，逻辑主语是forest

dianecarton

 as sources of building material and firewood是插入语前后用逗号隔开，修饰forests

撇开插入语不看就发现了明显的and平行结构