20km every 1 hr is what 20km/hr means.
so 3hrs is 20km*3=60km.
] Ceres is composed of rock and ice and is estimated to comprise approximately one third of the mass of the entire asteroid belt. Ceres is the only object in the asteroid belt known to be rounded by its own gravity (though detailed analysis was required to exclude 4 Vesta). From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, peaking once every 15 to 16 months,[21]hence even at its brightest it is too dim to be seen with the naked eye except under extremely dark skies.
Answer:

Explanation:
= Mass of the Earth = 5.972 × 10²⁴ kg
G = Gravitational constant = 6.67 × 10⁻¹¹ m³/kgs²
r = Radius of Earth = 6371000 m
m = Mass of person
The force on the person will balance the gravitational force

The acceleration that the Earth will feel is 
I think it is because the electrons repel each other
Let's start with an infinitive: it has a form "to..." - only sentences C and D have a phrase like this, so we can exclude other options.
Among those, C does not have a gerund, which is a verbal form: "dreaming" has a function of a noun there.
So the correct answer is the remaining one, D.