请教: 大全 sec2 - 4

In cold-water habitats, certain invertebrates and fish convert starches into complex carbohydrates called glycerols, in effect manufacturing its own antifreeze.fficeffice" />

(A) in effect manufacturing its own antifreeze

(B) effectively manufacturing antifreeze of its own

(C) in effect manufacturing their own antifreeze

(D) so that they manufacture their own antifreeze（C）

(E) thus the manufacture of its own antifreeze

请教这里的in effect做何解？修饰manufacturing是什么意思？

    longman上只查到in effect,(comma)的用法。