Q5. Two masses, each 5 kg, are attached to the two ends of a spring of spring
constant 40 N/m. The masses are pulled
away from each other and the spring gets
stretched by a length 20 cm . Work done
by the spring on each mass, is

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.