Consider the following portfolios:

1. 50% in Govt bonds, 50% in share W
2. 50% in share W, 50% in share X, where the returns are perfectly positively correlated
3. 50% in Government bonds, and 50% in the market portfolio
4. 50% in share X, 50% in share Y, where the returns are uncorrelated
5. 50% in share Y, 50% in share Z, where the returns are perfectly negatively correlated

In which of these portfolios would the standard deviation of the portfolio lie exactly midway between the standard deviations of the two securities?

a.1, 2, 3

b.1, 2, 3, 4

c.3, 4, 5

d.1, 2, 4

e.2, 4, 5