Final Answer:
The prefix "kilo-" signifies a thousandfold increase, aligning with the one million times greater conductivity described in the question. Thus, the correct option is d) kilo-
Step-by-step explanation:
The prefix "kilo-" is used to denote a factor of a thousand, and when dealing with measurements, it implies a multiplication by 1,000. In the context of the question, where nanotubes are described as being more than one million times more conductive, this aligns with the use of the kilo- prefix. To elaborate, one million is equivalent to 1,000,000, and since "kilo-" denotes a thousand, multiplying a base value by one million is the same as multiplying it by 1,000 (kilo-) a thousand times. Therefore, kilo- is the appropriate prefix for expressing a million-fold increase.
In mathematical terms, if we represent the base conductivity of the current materials as C, then the increased conductivity with nanotubes would be 1,000,000 times C, which can be expressed as 1,000,000C. The use of "kilo-" corresponds to this factor of a million, highlighting the significance of the conductivity improvement. In essence, the kilo- prefix provides a concise and standardized way of expressing large multiples in the metric system, making it a suitable choice for indicating a millionfold increase in conductivity in the given scenario.
In summary, the correct answer is (d) kilo-, as it accurately reflects the millionfold improvement in conductivity observed with the nanotubes in comparison to current materials used in airplane skins.
Therefore, the correct option is d) kilo-