Which one of the following molecules contains both ionic and covalent bonds?

Which one of the following is most acidic?

An infinite number of electric charges each equal to $5 \text{ nC}$ (magnitude) are placed along the $X$-axis at $x=1 \text{ cm}, x=2 \text{ cm}, x=4 \text{ cm}, x=8 \text{ cm} \dots$ and so on. In this setup, if the consecutive charges have opposite signs, then the electric field in $\text{N/C}$ at $x=0$ is: $\left(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \text{ N} \cdot \text{m}^2/\text{C}^2\right)$

If $p$ and $q$ are distinct prime numbers and if the equation $x^2 - px + q = 0$ has positive integers as its roots,then the roots of the equation are

If $PM$ is the perpendicular from $P(2, 3)$ onto the line $x+y=3$,then the coordinates of $M$ are

Which element is responsible for the crimson red color in fireworks?