Why can't all the mixtures be classified as solutions? a. not all mixtures are heterogeneous b. not all mixtures are homogeneous c. not all mixtures have solutes and solvents d. mixtures are made of only one substance.

C because A solution is a homogenous mixture at the molecular or ionic level of two or more pure substances that do not react with each other, whose components are in variable proportions.1 2 It can also be defined as a homogeneous mixture formed by a solvent and for one or several solutes.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.