What does orthoboric acid contain?

If the magnitudes of $a, b$ and $a+b$ are respectively $3, 4$ and $5$, then the magnitude of $(a-b)$ is

$A$ positively charged $(+q)$ particle of mass $m$ has kinetic energy $K$ and enters a region with a horizontal magnetic field $\overrightarrow{B}$ in a vertically downward direction. The acceleration of the particle is:

Assertion $(A)$: White tin is an example of a tetragonal system.
Reasoning $(R)$: For a tetragonal system,$a=b=c$ and $\alpha=\beta=\gamma \neq 90^{\circ}$. The correct answer is

If the tangent at point $(1, 2)$ on the curve $y = ax^2 + bx + \frac{7}{2}$ is parallel to the normal at point $(-2, 2)$ on the curve $y = x^2 + 6x + 10$,then:

During meiosis $I,$ the chromosomes start pairing at