Final answer:
The rate of the additional tax assessed on net investment income when it exceeds specified thresholds is 3.8% (option d).
Step-by-step explanation:
The rate of the additional tax that is assessed on net investment income when it exceeds specified thresholds is 3.8% (option d).
The additional tax, known as the Net Investment Income Tax (NIIT), is imposed on individuals with high incomes and certain types of investment income.
It is important to note that the rate of the NIIT may change based on the current tax laws, so it is always a good idea to consult the latest tax regulations or seek advice from a tax professional.