Final answer:
Arnold's likely filing status for the tax year 2016 is Single, as he is separated from his wife and his son does not qualify as a dependent.
Step-by-step explanation:
The student has asked about Arnold's filing status for the tax year 2016. Given that Arnold's wife, Sybil, abandoned him in 2015 and he has not seen or communicated with her since April of that year, he may not qualify for filing jointly. In addition, since their son, Evans, is 25 years old and earns over $6,000 each year, he does not qualify as a dependent child for tax purposes. Therefore, Arnold's likely filing status for the tax year 2016 is Single.