Hydrophilic sols are

The driver of a car travelling with speed $30 \,m/s$ towards a hill sounds a horn of frequency $600 \,Hz$. If the velocity of sound in air is $330 \,m/s$,the frequency of reflected sound as heard by the driver is ........ $Hz$.

For the reaction sequence given below, the correct statement$(s)$ is$($are$)$
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$($In the options, $X$ is any atom other than carbon and hydrogen, and it is different in $P , Q$ and $R )$

Which of the following supports a dense population of plankton and littoral vegetation?

In a permanent magnet at room temperature,