Under certain conditions the solid and liquid states of water can exist in equilibrium how are these conditions indicated on the phase diagram for water

in the phase diagram the line between solid and liquid is where both phases available at the same time

The phase diagram of water has following features

a) Triple point : this is the point of intersection of three curves and is the point where all the three phases of water exist together

The triple point of water is 273.16K, and 4.58 mm Hg

b) Curves : these represents the presence of two phases together

the curve is shared by any two phases

i) melting curve : shared between liquid and solid phase of water

ii) vapour curve : shared between liquid and gas phase

iii) sublimation curve: shared between solid and gas phase of water

c) area : these are the portions of a phase diagram which represent single phase of water : solid, liquid or gas

Thus answer is :

Curves are used to indicate that the solid and liquid states of water can exist in equilibrium

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a