As nothing is mentioned about employee number is in hundred or in thousand, I'm assuming it is in thousand (by seeing the given options)
In Jan, the total number of employees are $10$
Whereas, in Nov, the total number of employees is $16$
So, in the given period means from Jan-Nov Company takes a total of $(16-10)= 6$ which means $6,000$ employees.
And, among the given options the closest number of $6000$ is $5800$ which is Option C)
∴ Answer is Option C)