Final answer:
The left end of the rod will have a negative charge due to the accumulation of electrons, while the right end will have a positive charge due to the lack of electrons, resulting in (a) left end negative and right end positive.
Step-by-step explanation:
If we imagine a scenario as described—where electrons move to the left under the influence of an electric field, thus constituting an electric current to the right—we can deduce the net charges at the ends of the rod based on electron movement. As electrons accumulate at the left end of the rod due to their motion, that end will become negatively charged. Conversely, as electrons leave the right end of the rod, it will become relatively deficient in electrons, and thus positively charged. Therefore, the correct answer to the question of what the net charge on the right and left ends of the rod will become after the electric current flows to the right for a short time is (a) left end negative and right end positive.