Choose the best answer.
Which sentence correctly identifies an adjective phrase?

A. The discovery which was first of it's kind, "in several years", caused an international stir.

B. "The discovery", which was the first of its kind in several years caused an international stir.

C. The discovery, "which was the first of its kind in several years", caused an international stir.

D. The discovery whcih was the first of its kind in several years, "caused an international stir."

(The "" represent the underlined adjective phrase)