Antibody molecules a. have all of these characteristics. b. have a variable region that can activate complement or attach to macrophages. c. have a constant region that binds to antigens. d. are called gamma globulins or immunoglobulins. e. are large glycolipids.

b) Have a variable region that can activate complement or attach to macrophages.

Explanation:

Antibody:

Antibodies are the part of immune system that is protein in nature and  produced to protect body from pathogens such as bacteria and viruses. These pathogens are recognized through the fragment antigen-binding variable region. Antibodies are also known as immunoglobulin.

Gamma globulins are the class of globulins, Antibodies are the most significant gamma globulins but it should be remember that some antibodies are not gamma globulins.

Correct

On the basis of above knowledge discussed the correct answer of this question is option b i.e Have a variable region that can activate complement or attach to macrophages.

what's the rest of the question

not only is it colder, it also becomes darker, less salty, and more dense.