Questions

The meanings of the given words are as follows:
Zealous: having or showing zeal
Droopy: hanging down limply
Gigantic: of very great size or extent; huge or enormous
Tenacity: the quality or fact of being able to grip something firmly; grip
Assiduity: constant or close attention to what one is doing
Fervent: having or displaying a passionate intensity
Apathetic: showing or feeling no interest, enthusiasm, or concern
Conceited: excessively proud of oneself; vain
Capacious: having a lot of space inside; roomy
Hilarity: extreme amusement, especiallywhen expressed by laughter
Livid: furiously angry
Therefore, it can be observed that option C i.e. ‘fervent, apathetic’ forms a synonym- antonym pair of ‘zealous’.

Deficiency of Iodine cause Goiter also called Enlarged Thyroid. It doesn't give any pain but difficult to swallow and breath are its causes.

QRP

The correct order of evolutionary history from the above given options is jellyfish, reptiles, mammals.