What is necessary in order for clouds to form when the atmosphere is absolutely stable? cooling of the air mass from below
a lifting mechanism other than convection (such as a front)
an environmental lapse rate less than 5°c
a high degree of subsidence

The correct option here is the first one.

Explanation:

Precipitation or humidity present in air or we can say the most air tends to rise above. And becomes colder and colder such that after a certain limit.  While the air can no longer take the weight of this water present in air bus resulting in condensation of water.

The pressure of colder air from below is necessary for cooler pushing it above, only this pressure by air can lead to formation of Clouds.

answer: option (b) is the correct answer.

explanation:

a covalent bond is formed by sharing of electrons. whereas polarity arises due to difference in electronegativity of two atoms.

therefore, more is the electronegativity of an atom which combines with the titanium, more readily it will induce a partial positive and negative charge.

thus, out of the given options fluorine is most electronegative and has an incomplete octet. therefore, it will readily combine with titanium to share the electrons and complete its octet.  

answer: e.   sour taste

explanation: acids are those substances which dissociates in water to give ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. acids are sour in taste. example: hcl

bases are those substances which dissociates in water to give ions or accepts ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. bases are bitter in taste. bases are slippery in nature.