Which of the following are not correct?
(i) The basic unit of time is second.
(ii) Every object moves with a constant speed.
(iii) Distances between two cities are measured in kilometers.
(iv) The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/h.

We know that,

(i) Time is a moment or duration in which things occur. We measure time with the help of clocks and watches. The basic or SI unit of time is second (s).

(ii) Distance covered by an object in a unit time as the speed of the object. Speed of an object may or may not varies. It means that speed can’t be always constant.

(iii) Distance is the total movement of an object without any regard to direction. The distance between two cities are measured in kilometres (km). It is big unit of distance.

(iv) The time taken by the pendulum to complete one oscillation is called its time period. The time period of a given pendulum is always constant because it depends on the length of the pendulum.

(v) Distance covered by an object in a unit time as the speed of the object. The speed of a train is measured in km/h and in m/s.

So, we can say that, (ii), (iv) and (v) are not correct statements.