In the given sentences, we are identifying whether the nouns are singular or plural.
The window's frame was covered with dust.
The noun here is 'window's frame'. The apostrophe 's' shows possession, referring to the frame of one window. Therefore, it is singular .
Chosen option: (a) singular
The auditorium echoed with the singers' voices.
The noun here is 'singers' voices'. The apostrophe after 'singer' indicates possession and it refers to multiple singers. Therefore, it is plural .
Chosen option: (b) plural
The cuckoos' songs were melody to the ears.
In this case, 'cuckoos' songs' indicates that the songs are owned by more than one cuckoo. The apostrophe after the 's' shows this plural possession, making it plural .
Chosen option: (b) plural
My brother's cupboard is arranged neatly.
Here, 'brother's cupboard' shows that the cupboard belongs to one brother, using an apostrophe 's'. Thus, the noun is singular .
Chosen option: (a) singular
Vinit searched for the visitor's bag all over the room.
In this sentence, 'visitor's bag' suggests that the bag belongs to one visitor, indicated by the apostrophe 's'. Therefore, it is singular .
Chosen option: (a) singular
In summary, possessive forms in English help clarify ownership and whether the owner is singular or plural, using apostrophes appropriately based on the context.