Fill in the blanks with the most appropriate option:-

River, valleys and coastal plains constitute __________ a third of the country.

approximately

The most appropriate option to fill in the blanks is approximately.

The sentence "River, valleys and coastal plains constitute approximately a third of the country" means that river, valleys and coastal plains make up about a third of the country's landmass. The other options are not appropriate because they do not convey the same meaning.

• The word "outlandishly" means in a very strange or unexpected way. This does not make sense in the context of the sentence, as there is nothing strange or unexpected about river, valleys and coastal plains making up about a third of the country's landmass.
• The word "precisely" means exactly. This does not make sense in the context of the sentence, as it is impossible to know the exact percentage of landmass that is made up of river, valleys and coastal plains.
• The word "minimally" means to the smallest possible extent. This does not make sense in the context of the sentence, as river, valleys and coastal plains make up a significant portion of the country's landmass.