Je suis ne _ Nigeria.

The sentence Je suis ne ___ Nigeria means "I was born in Nigeria." This question tests the use of prepositions before country names in French.

The correct preposition is au. In French, the choice of preposition before a country depends on the country's grammatical gender:

• en is used before feminine countries (e.g., en France, en Chine) and masculine countries beginning with a vowel (e.g., en Iran)
• au is used before masculine countries beginning with a consonant (e.g., au Japon, au Canada)
• aux is used before plural countries (e.g., aux Etats-Unis)

Le Nigeria is a masculine country name beginning with a consonant, so the correct preposition is au (contraction of a + le).

The other options are incorrect:

• a alone is not used before country names that take an article
• dans means "in/inside" and is not the standard preposition for countries
• en would be correct for feminine countries, but le Nigeria is masculine

The complete sentence is: Je suis ne au Nigeria - I was born in Nigeria.