The question asks about the official currency used in Bhutan. To determine the correct answer, we need to identify the official currency of Bhutan among the given options.

Let's evaluate the options one by one:

• Bhutanese Taka: The currency 'Taka' is associated with Bangladesh, not Bhutan. Hence, this is incorrect.
• Bhutanese Dollar: Bhutan does not use 'Dollar' as its currency. So, this is incorrect.
• Bhutanese Rupee: 'Rupee' is commonly associated with India and other South Asian countries but is not the official currency of Bhutan.
• Bhutanese Ngultrum: The 'Ngultrum' is the official currency of Bhutan and is represented by the symbol 'Nu' and the code 'BTN'. The Ngultrum is pegged equal to the Indian Rupee and they are often used interchangeably in Bhutan.

Based on the evaluation of the options, the correct answer is: Bhutanese Ngultrum, as it is the officially recognized currency of Bhutan.

Hence, the correct answer is Bhutanese Ngultrum.