Which of the following is not true of color blindness?
1. a color blind person cannot see any colors.
2. color blind people learn to rely on shapes, patterns, and positions of signs and signals.
3. for some people, it might be difficult to recognize colors of traffic lights and signs.
4. red-green color blindness is the most common type of color blindness.

Identify the correct relation showing that the radius r of the orbit of a moon of a given planet can be determined from the radius r of the planet, the acceleration of gravity at the surface of the planet, and the time τ required by the moon to complete one full revolution about the planet. determine the acceleration of gravity at the surface of the planet jupiter knowing that r = 71 492 km and that t= 3.551 days and r= 670.9 × 10^3 km for its moon europa.