ANS:A - 10000

When we talk about parts per million (ppm), we are expressing a concentration level where 1 ppm is equivalent to 1 part of the substance per million parts of the whole. Now, to convert from a percentage to parts per million, we multiply the percentage value by 10,000. This conversion arises from the fact that 1% is equal to 10,000 ppm. Here's how the conversion works: 1% = 1 part per hundred = 11001001​ And 1 part per hundred (1%) is equivalent to 10,000 parts per million (ppm), since: 1100×10,000=100 ppm1001​×10,000=100ppm So, when we say that 1% concentration of water vapor in air is equivalent to 100 ppm, it means that for every million parts of air, there are 100 parts that consist of water vapor.