c A signed char value.
i A signed integer value.
(This 'integer' is at least 32 bits wide. Its exact
size depends on what a local C compiler calls 'int',
and may even be larger than the 'long' described in
the next item.)
The question asks specifically for signed 8-bit, which is "c", a signed char value (8 bits). "At least 32 bits" is not 8 bits.