Which of the following is a Lewis acid?

Which of the following radioactive isotopes is used in the detection of thyroid cancer?

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:

Which of the following statements is correct?

Identify the incorrect statement among the following.

$A$ wire of resistance $4\,\Omega$ is stretched to twice its original length. The resistance of the stretched wire would be ................ $\Omega$.