Classical biotechnology dates back about years ago.
a.100
b.1,000
c.10,000
d.100,000

The correct answer should be C. 10,000. Although it sounds like something futuristic, it's existed almost as long as civilzied humans because it was present in the form of selective breeding of animals and plants during the early eras of agriculture and settling in river valleys. Nowadays it's more complex and more things can be achieved.

Cr(oh)3 -> cr(3+) + 3oh-