In 1881, French chemist Camille Faure redesigned the rechargeable lead-acid battery. Faure’s design greatly increased the
amount of electricity that the original battery, which the French physicist Gaston Planté ______ ﬁfteen years earlier, could
hold.
is inventing
will invent
invents
had invented
Choice D is the best answer. Faure redesigned the battery in 1881, and the original battery was invented “ﬁfteen years
earlier.” Notice that this is the only choice in the past tense. To indicate that a past occurrence took place before another
past occurrence, we need to use “had” + the past tense form of the verb. This is called the “past perfect” tense.
Choice A is incorrect. This choice creates a tense error. Planté invented the original battery in the past, so we shouldn’t use
the present tense “is inventing.” Choice B is incorrect. This choice creates a tense error. Planté invented the original battery in
the past, so we shouldn’t use the future tense “will invent.” Choice C is incorrect. This choice creates a tense error. Planté
invented the original battery in the past, so we shouldn’t use the present tense “invents.”