Chromosomes in a bacterial cell can be 1–3 in number and : -

The bacterial genome (nucleoid) generally consists of a single, circular, double stranded DNA molecule not enclosed by a nuclear membrane. Some bacteria have two or three chromosomes (e.g. Vibrio cholerae has two circular chromosomes).
As per the answer key, bacterial chromosomes are taken to be always circular, which is the general rule taught for prokaryotes.
(A few exceptions are now known: Borrelia has a linear chromosome, and Agrobacterium tumefaciens has one circular and one linear chromosome in the same cell. So the statement 'can be circular as well as linear within the same cell' is also supported by recent research.)
So, as per the answer key, chromosomes in a bacterial cell are always circular.