Indifference Curves for Risk-Averse Investors/ Various Types of Investors

in the Curriculum Volume 4, Page 298 the Exhibit 11 shows the indifference curves for risk-averse investors. Curve 1> 2>3, it is understanble. however seems the difference of three curves are caused by risk free rate, means the expected rate when risk is zero.

And in terms of Exhibit 12 in the next page, I can’t understand why the curve of risk neutral is a horizon line with 0 slope. it is not understable. thanks.