The correct answer to the question is option 1, which states that the stain was due to oil. This can be inferred from the fact that only lipase, an enzyme that specializes in breaking down fats and oils, was able to completely remove the stain. Lipase works by breaking down the ester bonds present in fats and oils, which makes it effective at removing oil-based stains.

Option 2 states that the stain was due to protein. However, if this were the case, trypsin, an enzyme that specifically breaks down proteins, would have been able to remove the stain as well. Since trypsin did not work, option 2 can be ruled out.

Option 3 suggests that the stain was a mixture of protein and oil. However, as mentioned earlier, if protein was the main component of the stain, trypsin would have been effective as well. Therefore, option 3 is also not supported by the evidence provided.

Option 4 states that the stain was due to starch containing plant pigment. This can be ruled out because none of the enzymes used in the experiment were specifically capable of breaking down starch or plant pigments.

In conclusion, based on the information provided, option 1 - oil - is the most likely explanation for the