Which of the following expressions could be used to create a calculated field called gigabytes?

Option A omits the pipe character and the equals sign assignment, making 'eval sc_bytes(1024/1024)' syntactically invalid SPL that cannot create a field.

Option B uses the correct Splunk eval syntax '| eval fieldname=expression', which is the only syntactically valid structure among the choices for defining a calculated field. This format - a pipe followed by eval, a field name, an equals sign, and an arithmetic expression - is exactly what Splunk requires to evaluate and assign a new field value.

Option C omits both the pipe character and the 'eval' keyword entirely; a bare 'fieldname=expression' string is not valid SPL and will not be interpreted as a field calculation.

Option D contains only an arithmetic expression fragment with no pipe, no eval keyword, and no field name assignment, making it completely invalid as an SPL statement.