Questions

'Are’ needs to be replaced with ‘is’ to make the sentence contextually correct. This is because, ‘in subject verb agreement, we match the subject with the nearest verb or the verb with the nearest or the first subject. But the verb should be matched with the main subject of the sentence’. Here the main subject is ‘Ignorant’ which is singular and so is followed by a singular verb.

Nostoc is a prokaryote. Prokaryotic cells lack membrane bound organelles and well organized nucleus, that is nuclear envelope is absent in these cells.

The nuclear envelope, also known as the nuclear membrane, a bilayer membranes which surrounds the nucleus, and in eukaryotic cells it encases the genetic material.

Papayas are yellow due to the presence of carotene and xanthophyll pigments i.e, Caricaxanthin present in the chromoplasts of the fruit pulp.

The coloration of the different tissues in plants is due to the plastids which are present in the cells. Leucoplasts are white in colour, chloroplasts are green in colour and chromoplasts are of various colours. These plastids can take any colour at different time. Therefore, green fruits ( chloroplasts) turn colurful (chromoplasts) at maturity.

‘Cured’ is followed by the preposition ‘of’. Thus, the correct sentence would be, ‘He will be cured of his fever’.

A sinkhole (in Karst topography) is a hole in the ground that forms when water dissolves surface rock. Often, this surface rock is limestone, which is easily eroded, or worn away, by the movement of water.

Formation of a Sinkhole: In a landscape where limestone sits underneath the soil, water from rainfall collects in cracks in the stone. These cracks are called joints. Slowly, as the limestone dissolves and is carried away, the joints widen until the ground above them becomes unstable and collapses. The collapse often happens very suddenly and without very much warning. Water collects in these collapsed sections, forming sinkholes.

Sinkholes also form when the roofs of caves collapse. Sinkholes are often funnel-shaped, with the wide end open at the surface and the narrow end at the bottom of the pool.Sinkholes vary from shallow holes about 1 meter (3 feet) deep, to pits more than 50 meters (165 feet) deep.