for an atom’s electrons, how many energy sub levels are present in the principal energy level n = 4?

Amagnetic field "does not" interact with stationary electric charges. so, a.hope my answer you : )

Ithink the answer is d

The boat's velocity relative to the riverbank can be resolved into two components. the component going north is 2.7 m/s and the component going west is 1.2 m/s.we add these two vectors and then find the magnitude of the resultant to get the speed.the magnitude of the resultant vector from adding can be obtained by the pythagorean theorem.    to two significant figures, the boat's speed relative to the riverbank is 3.0 m/s.

Chope i i hope i did