Which of the following comparisons is incorrect? a. talc is softer than gypsum. b. feldspar is harder than calcite. c. quartz is softer than corundum. d. apatite is harder than topaz.

Option (d) is the correct answer.

Explanation:

Mohs scale is used to classify minerals on the basis of their hardness. This scale includes 10 minerals. The hardness of each of the minerals is as follows.

Talc = 1Gypsum = 2Calcite = 3Fluorite = 4Apatite = 5 Orthoclase Feldspar = 6Quartz = 7Topaz = 8Corundum = 9Diamond = 10

Therefore, more is the number given to a mineral, more will be its hardness.

Thus, we can conclude that out of the given options the comparison Apatite is harder than topaz is incorrect because Apatite is softer than topaz according to Mohs scale.

Answer is to avoid experimental error

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .