Which of the following is a method of sexual reproduction in algae?

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

$A$ block rests on a rough inclined plane making an angle of $30^o$ with the horizontal. The coefficient of static friction between the block and the plane is $0.8.$ If the frictional force on the block is $10\,N,$ the mass of the block (in $kg$) is (take $g = 10\,m/s^2$)

The area (in square units) of the triangle formed by $x+y+1=0$ and the pair of straight lines $x^2-3xy+2y^2=0$ is

Which of the following is the strongest reducing agent?

Two waves having intensity $I$ and $9I$ produce interference. If the resultant intensity at a point is $7I$,the phase difference between the two waves is.....$^o$