A riskfree asset (a) has a return correlation coefficient with securities of 1. (b) has a negative return covariance with each security. (c) has a standard deviation of return of zero. (d) has a positive return covariance with many securities. (e) has a return correlation coefficient with securities of -1.

C) Has a standard deviation of return of zero

Step-by-step explanation:

A riskfree asset is one in which return is certain in the future. With a standard deviation of zero, it means that there is certainty for return in investment.

F(x)=a(x-h)²+k
the axis of symmetry is x=h
the vertex is (h,k)
if a<0, the parabola opens down and has a max
if a>0, the parabola opens up and has a minimum

so

f(x)=-3(x-6)²-11
a=-3<0 so it opens down and has a maximum
h=6, the axis of symmetry is x=6
k=-11
vertex is (6,-11)

so answers are
axis of symmetry is the line x=6
the parabola opens down
the value of h, when the equation is written in vertex form, is positive