When examining economic growth rates throughout history?
a. the world experienced little to no growth until the industrial revolution, after which all of the world's economies began to experience real economic growth.
b. almost no growth occurred prior to 1300 ad and then all countries of the world grew at a rapid pace.
c. it appears that the world experienced consistent growth since records have been kept.
d. the world experienced little to no growth until the industrial revolution, after which some economies began to experience real economic growth.

Stocks a, b, and c are similar in some respects: each has an expected return of 10% and a standard deviation of 25%. stocks a and b have returns that are independent of one another; i.e., their correlation coefficient, r, equals zero. stocks a and c have returns that are negatively correlated with one another; i.e., r is less than 0. portfolio ab is a portfolio with half of its money invested in stock a and half in stock b. portfolio ac is a portfolio with half of its money invested in stock a and half invested in stock c. which of the following statements is correct? a. portfolio ab has a standard deviation that is greater than 25%.b. portfolio ac has an expected return that is less than 10%.c. portfolio ac has a standard deviation that is less than 25%.d. portfolio ab has a standard deviation that is equal to 25%.e. portfolio ac has an expected return that is greater than 25%.