Which of the following statements is  not  true regarding physical properties and changes?                 a.  a series of physical changes, such as filtration and heating, can be used to separate substances with different physical properties.      b.  physical changes include evaporating, boiling, and dissolving.      c.  physical properties can be observed without any change in the substance's identity.      d.  physical changes can change compounds into elements.

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%.