Philosophy of Logic Homework

Can someone help me distinguish arguments from nonarguments and identify a conclusion from the multiple choice below?:

"Lead is toxic, but do you know why? Lead is toxic mainly because it preferentially replaces other metals in biochemical reactions. In doing so, it interferes with the proteins that regulate blood pressure (which can cause development delays in children and high blood pressure in adults), heme production (which can lead to anemia), and sperm production. Lead also displaces calcium in the reactions that transmit electrical impulses in the brain, which diminishes the ability to think and recall information." (Helmenstine, Anne Marie. "Your Guide to Chemistry." About.com. 3 March 2006. <http://chemistry.about.com/od/howthingsworkfaqs/f/leadpoisoning.htm>.)

A - Argument; conclusion: It interferes with the proteins . . . and sperm production.

B - Argument; conclusion: Lead is toxic.

C - Nonargument.

D - Argument; conclusion: It preferentially replaces other metals in biochemical reactions.

E - Argument; conclusion: Lead also displaces calcium . . . recall information.