Which was the first commercially developed insecticide?

When a wave traverses a medium,the displacement of a particle located at $x$ at a time $t$ is given by $y = a \sin (bt - cx)$,where $a, b,$ and $c$ are constants of the wave. Which of the following is a quantity with dimensions?

$A$ metal which does not react with nitrogen is

The type of bonds present in sulphuric anhydride $(SO_3)$ are:

How many meiotic divisions are required to produce $100$ grains of wheat?

Two identical thin bar magnets,each of length $l$ and pole strength $m$,are placed at a right angle to each other with the north pole of one touching the south pole of the other. The magnetic moment of the system is: