Answer:
A. Warning
Explanation:
Out of all said choices, the best choice would be warning since it would fit the sentence the most.
"A Warning notifies you that danger is present." compared to:
"A Hazard notifies you that danger is present."
"A Safety notifies you that danger is present."
"A Danger notifies you that danger is present."
Answer:
Pb(NO3)2 + KI = KNO3 + PbI2
Answer : The reaction is endothermic.
Explanation :
Formula used :

where,
= change in temperature = 
Q = heat involved in the dissolution of KCl = ?
m = mass = 0.500 + 50.0 = 50.5 g
c = specific heat of resulting solution = 
Now put all the given value in the above formula, we get:


The heat involved in the dissolution of KCl is positive that means as the change in temperature decreases then the reaction is endothermic and as the change in temperature increases then the reaction is exothermic.
Hence, the reaction is endothermic.
The answer to this question is A- evaporation