why are sedimentary rocks more difficult to directly date than igneous or metamorphic rock? group of answer choices they often do not contain the right radioactive isotopes to measure they are usually composed to sediments of preexisting rock, so any ages obtained represent the age of the rocks that weathered to produce them. they are less common than igneous and metamorphic rock. they fall apart too easily because they are generally weaker rocks than igneous or metamorphic rocks