As you increase the number of securities in a portfolio:

a. The number of variance and covariance terms both increase in a linear manner.

b. The number of variance terms increases in a linear manner, but the number of covariance terms increases in a geometric manner.

c. The number of covariance terms increases in a linear manner, but the number of variance terms increases in a geometric manner.

d. The number of variance and covariance terms both increase in a geometric manner.