Answer:
B. gas mixed with a liquid
Explanation:
because:
A. a solid can't dissolve in a liquid.
C. two liquids mixed isn't a solution
D. Not All of the above for sure.
Answer:
The common application of indicators is the detection of end points of titrations. The colour of an indicator alters when the acidity or the oxidizing strength of the solution, or the concentration of a certain chemical species, reaches a critical range of values.
It is iron
Hope that helps :))