Which of the following sets of concurrent forces may be in equilibrium?

Three concurrent co-planar forces $1 \,N$,$2 \,N$,and $3 \,N$ acting along different directions on a body:

Two like parallel forces $20 \,N$ and $30 \,N$ act at the ends $A$ and $B$ of a rod $1.5 \,m$ long. The resultant of the forces will act at the point ........

Mr. $A, B$ and $C$ are trying to put a heavy piston into a cylinder at a mechanical workshop in a railway yard. If they apply forces $F_1, F_2$ and $F_3$ respectively on ropes,then for which set of forces at that instant will they be able to perform the said job?

$A$ block is being pulled by a force $F$ on a long frictionless level floor. The magnitude of the force is gradually increased from zero until the block lifts off the floor. Immediately after the block leaves the floor,its acceleration is

$A$ mass $M$ is suspended by a rope from a rigid support at $A$ as shown in the figure. Another rope is tied at point $B$,and it is pulled horizontally with a force $F$. If the string $AB$ makes an angle $\theta$ with the vertical in equilibrium,then the tension in the string $AB$ is: