The correct answer is B. was. Dollars are considered a singular unit here in the U.S. and thus follow the was/is rule.
The earlier version didn't have all the words in it
One of the inventions which transformed the field of electricity is the light bulb.
<u>Explanation:</u>
One of the inventions that affected the society was the invention of the light bulb which transformed the field of light and electricity.
With the invention of the light bulb, the risk of the building fires from the gas lighting, kerosene lighting was all taken away. Thus it lessened the risk of explosion. The disadvantages of a candle also went away with the invention of the candle.
