Which sentence correctly forms the plural of 1940?

a.
in the early 1940s', the japanese launched an attack on pearl harbor.

b.
in the early 1940's, the japanese launched an attack on pearl harbor.

c.
in the early 1940s, the japanese launched an attack on pearl harbor.

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.

the correct answer would be a