Explanation:

Igneous rocks contain a large amount of fossils: This statement is incorrect. Igneous rocks are formed from the cooling and solidification of molten magma or lava, and they do not typically contain fossils. Fossils are more commonly found in sedimentary rocks.

Plutonic rocks have larger crystals, and volcanic rocks have smaller crystals: This statement is correct. Plutonic rocks, also known as intrusive rocks, cool and solidify below the Earth's surface, allowing for the formation of larger crystals. Volcanic rocks, or extrusive rocks, cool quickly on the Earth's surface, leading to the formation of smaller crystals.

Most igneous rocks are hard: This statement is generally correct. Igneous rocks can vary in hardness, but many of them are indeed hard and resistant due to their mineral composition.