Which of the following is a valid mathematical statement?

If the straight lines $2x + 3y - 1 = 0$,$x + 2y - 1 = 0$ and $ax + by - 1 = 0$ form a triangle with the orthocentre at the origin,then $(a, b) =$

In which plant group are the sporophylls arranged spirally along an axis to form distinct compact structures called strobili or cones?

The area (in square units) of the region enclosed by the two circles $x^2+y^2=1$ and $(x-1)^2+y^2=1$ is

If the impurity in a metal has a greater affinity for oxygen and is more easily oxidised than the metal,then the purification of metal may be carried out by

Let $z=x+iy$ be a complex number where $x$ and $y$ are integers. Then the area of the rectangle whose vertices are the roots of the equation $z\bar{z}^3+\bar{z}z^3=350$ is