These crystals sparkle with the lustrous sheen we think of metals having. They are extremely good conductors of heat and electricity. The melting point of these crystals depends on the metal used in the crystal. Is true?

i think so it’s will be b yes i believe its

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

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.