Passage

Bar codes appear on all kinds of merchandise, from groceries to baseball caps. When an item's bar code is read by a scanner, information including the item's price is conveyed electronically. In the late $1950$ s$,$ before modern bar codes, David Collins developed a similar technology for identifying train cars as they passed through a station. Patterns of blue and yellow stripes painted on the sides of train cars reflected light, which was picked up by a sensor$.$ His invention, however, was not as efficient as modern bar codes because dirt often covered the stripes and prevented them from reflecting light effectively.

Question

Which statement best expresses the main idea of the passage?

Bar codes help merchants keep careful track of sales

Modern bar codes have a less successful predecessor.

David Collins successfully marketed bar code technology to merchants.

Bar codes have been used in stores since the late $1950$ s$.$