Hello.
The answer is: A. keep a cork in the test tube so the solution cannot spill out
B and C both could be very deadly and it shouldnt be D because if u have an open flame you shouldnt open it even if its not towards anyone.
have a nice day
Explanation:
A physical change is one which can be reversed.it also does not produce any new substance.
changes in state such as the melting of a solid, the freezing and vaporization of a liquid as well as changes In shape are examples of physical changes
Positive ions or molecules that have lost one or more electrons where negative ions are actually oxygen atoms with extra negatively charged electrons.
Mined salt has sharp edges v s sea salt with rounded edged
Opioid's tend to show during runners high, so my guess would most likely be dopamine
