There was no D on the page. I am choosing E instead.
In order to choose the insignificant inventions, I simply thought about which inventions had the least amount of effect on society. For me, Aibo and the Monorail systems were very obviously insignificant. I have never heard of an Aibo and the Monorail is only used in a few places(ex: Disney). I struggled a bit with the Aerosol Spray(because of its wide use), however I believe that its abilities can be replicated by many other existing products.
In order to choose the most significant inventions, I did the opposite. I thought about which inventions had the most effect on society. These were far easier for me to decide because I use or am effected by the inventions I chose everyday. I use electronics and email all day every day. In fact, I am using an electronic device to complete this assignment. I check my email 10 times a day and send many emails in order to communicate with teachers and other students. Though I do not "use" explosives every day, everyone in the world is impacted by their use and impact of explosives and other such weapons.