Which of the following statements about marketing environment forces is correct?

A: They influence customers by affecting their lifestyles, standards of living, and preferences and needs for products.

B: They do not influence customers' reactions to a firm's marketing mix.

C: They fluctuate slowly and do not create threats to a firm's marketing mix.

D: They never fluctuate quickly.

E: They do not influence the way a marketing manager performs certain marketing activities.