With which of the following curves are different grades usually joined together?

Option 3 : Vertical

Explanation:

Vertical Curve:

•  A curve used to connect two different grade lines of railways or highways is called a vertical curve.
• A vertical curve may be Circular or Parabolic. the parabolic vertical curve is preferred more and invariably used.
• However, it is best to use a vertical curve having a constant rate of change of gradient i.e. a parabolic and as it turns out, parabolic vertical curves are easy to Calculate and used.

Transition curve:

• To minimize discomfort arising out of the sudden change in curvature at the junction of a tangent and a curve, a special type of curve is provided in between for gradual change from the back tangent to the circular curve and again from the circular curve to the forward tangent.
• This horizontal curve having varying radius is known as the transition curve.