Magnetic field is a quantity that has _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. The magnetic field lines emerge from _ _ _ _ _ _ _ _ _ _ _ pole and merge at _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ pole.
(A) Only magnitude, north, south.
(B) Only magnitude, south, north.
(C) Both magnitude and direction, south, north.
(D)Both magnitude and direction, north, south.

Hint:To answer this question,we must have knowledge about vector quantities,magnetic field and magnetic field lines.

Complete step by step answer:
Magnetic field is a vector quantity.
 A vector quantity is a quantity that has both magnitude and direction. It is typically represented by an arrow whose direction is the same as that of the quantity and whose length is proportional to the quantity's magnitude. Although a vector has magnitude and direction, it does not have position.So, the magnetic field has both magnitude and direction.
Since the magnetic field has direction, the direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it. Therefore it is taken by convention that the field lines emerge from the North Pole and merge at the South Pole. Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus the magnetic field lines are closed curves.
The main characteristics of magnetic field lines are:
In a single bar magnet, they attempt to form closed loops from pole to pole.
1)They never cross one another.
2)They all have the same strength.
3)Their density decreases with increasing distance from the poles.
4)They are considered to have direction as if flowing, though no actual movement occurs.
5)They flow from the south pole to the north pole within a material and north pole to south pole in air.
So, Option (D) is the correct answer.

Note:Sometimes there is a confusion between vector and scalar quantities so you must always remember that the quantities which only have magnitude is known as scalar while the quantities which have magnitude as well as direction is known as vector quantities.