Which of the following is absent in polluted water?

If $A$ and $B$ are two independent events such that $P(B)=\frac{2}{7}$ and $P(A \cup B^c)=0.8$,then $P(A)$ is equal to:

In the process of transcription,the sigma factor is important for:

$A$ rocket with a lift-off mass $2 \times 10^4 \ kg$ is blasted upwards with an initial acceleration of $5 \ m \ s^{-2}$. The initial thrust of the blast is (Take $g = 10 \ m \ s^{-2}$)

Which of the following cancers is caused by the consumption of tobacco?

The species having tetrahedral shape is