In which group of organisms do the cell walls form two thin overlapping shells that fit together?

Assertion : Silicones are hydrophobic in nature.
Reason : $Si-O-Si$ linkages are moisture sensitive.

Blood pressure in the pulmonary artery is

Which of the following is the most important cause driving animals and plants to extinction?

Observe the following statements:
$I$. If $dy + 2xy dx = 2e^{-x^2} dx$, then $ye^{x^2} = 2x + c$.
$II$. If $ye^{-x^2} - 2x = c$, then $dx = (2e^{-x^2} - 2xy) dy$.
Which of the following is a correct statement?

The periodic time of a particle doing simple harmonic motion is $4 \ s$. The time taken by it to go from its mean position to half the maximum displacement (amplitude) is