Which of the following is a vector quantity?

Charge $q$ is uniformly spread on a thin ring of radius $R.$ The ring rotates about its axis with a uniform frequency $f \ Hz.$ The magnitude of magnetic induction at the center of the ring is

Two long parallel wires are at a distance $2d$ apart. They carry steady equal currents flowing out of the plane of the paper,as shown. The variation of the magnetic field $B$ along the line $XX'$ is given by

$A$ circular coil carrying a certain current produces a magnetic field $B_{0}$ at its centre. The coil is now rewound so as to have $3$ turns and the same current is passed through it. The new magnetic field at the centre is

The magnetic field at the center of a current-carrying loop of radius $0.1 \ m$ is $5\sqrt{5}$ times that at a point along its axis. The distance of this point from the center of the loop is: (in $m$)

At a distance of $10\, cm$ from a long straight wire carrying current,the magnetic field is $0.04\, T$. At a distance of $40\, cm$,the magnetic field will be....$T$