If an indelible ink is used, this will not be . . . . . . .

The correct answer is D. obviated.

Obviate means to make something unnecessary or avoidable. In this case, if an indelible ink is used, the need to erase or remove the writing will be eliminated.

The other options are incorrect because:

• Observed means to watch or notice something. In this case, the writing will still be visible, so it will be observed.
• Obligated means to be required to do something. In this case, there is no obligation to erase or remove the writing, so it will not be obligated.
• Obliterated means to destroy or erase something completely. In this case, the writing will still be visible, so it will not be obliterated.