Which of the following cannot be used in Friedel-Crafts reactions?

Which of the following plants exhibits a haplontic life cycle?

The magnitude of maximum acceleration is $\pi$ times that of maximum velocity of a simple harmonic oscillator. The time period of the oscillator in seconds is

When acetylene is passed through a red-hot iron tube,compound $X$ is formed. Which one of the following reactions will yield $X$ as the major product?

Two point charges $-q$ and $+q$ are located at points $(0, 0, -a)$ and $(0, 0, a)$ respectively. The electric potential at a point $(0, 0, z)$,where $z > a$ is

$A$ magnet makes $40$ oscillations per minute at a place having a magnetic field of $0.1 \times 10^{-5} \, T$. At another place, it takes $2.5 \, s$ to complete one vibration. The value of the Earth's horizontal magnetic field at that place is: