The setting of cement is an: MCQ with Answer and Explanation

Explanation:
Rutherford's experiment led to the nuclear model of the atom, concluding that almost all the mass and positive charge are concentrated in a very small central nucleus, while electrons orbit around it. Option B is Thomson's model, A is Bohr's model, and D is de Broglie's concept.

Explanation:
Ozone (O₃) has a coordinate bond (dative bond). One oxygen atom donates a lone pair to another oxygen atom. The Lewis structure shows O=O⁺–O⁻ or resonance. NaCl is ionic; H₂O has polar covalent bonds; NH₃ has ordinary covalent bonds (though it can donate a lone pair to form coordinate bond in NH₄⁺).

Explanation:
Pure rainwater naturally has pH about 5.6 because CO₂ from air dissolves and forms carbonic acid. This is not considered acid rain. Acid rain has pH below 5.0 (due to SO₂ and NOₓ).