Growing crop plants in monoculture leads to ........

$A$ bag contains $6$ white and $4$ black balls. Two balls are drawn at random. The probability that they are of the same colour is:

The yellow colour solution of $Na_2CrO_4$ changes to orange-red on passing $CO_2$ gas due to the formation of

Which one of the following salts gives an acidic solution in water?

One litre of oxygen at a pressure of $1\, atm$ and two litres of nitrogen at a pressure of $0.5\, atm$ are introduced into a vessel of volume $1\, L$. If there is no change in temperature,the final pressure of the mixture of gas (in $atm$) is

Which organisms are primarily included as pests?