At what temperature is the boiling point of this substance

Option (c) is the correct answer.

Explanation:

Boiling point is defined as the temperature at which vapor pressure of a liquid becomes equal to the vapor pressure of its surrounding atmosphere.

In the given graph, boiling point of given substance is at 120 degree celsius.

And the horizontal line at 120 degree celsius shows that the liquid and vapor form of substance are in equilibrium with each other.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer