What would be the acceleration of gravity of a planet with four times the mass of earth but twice the radius?

-- Multiplying the mass by  4  multiplies the acceleration of gravity by  4 .

-- Doubling the radius multiplies the acceleration of gravity by (1/2²) = 1/4 .

-- Doing both multiplies the acceleration of gravity by  (4 / 4)  =  1 .

It doesn't change.  The acceleration of gravity on that planet
would be the same as it is on Earth.

The reflection of the candle in the concave mirror formed an upside-down virtual image that is smaller than the candle.in other words. the answer is the third option, c

The duration of a photographic flash is related to an rc time constantly