Which class of enzymes catalyzes reactions involving the formation of double bonds?

Lyases

Lyases are class of enzymes that catalyzes reactions involving the formation of double bonds.

Lyases are class of enzymes that catalyzes the joining of C-C ( carbon to carbon), C-O (carbon to oxygen), and C-N (carbon to nitrogen) bonds by hydrolysis or oxidation. These bonds are usually held by the process of elimination which leads to the formation of new double bonds or cyclical molecules. Examples of lyases include; aldolase and adenylate cyclase.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

the answer is c a tornado