Question

make a word that means \possible to be done sucessfully.\ achieve able ness ment

Explanation:

To form a word meaning "possible to be done successfully", we combine "achieve" with a suffix. The suffix "-able" is used to form adjectives meaning "capable of being...". So combining "achieve" and "able" gives "achievable", which means possible to be achieved (done successfully). The other options: "ness" is a suffix for nouns (e.g., "happiness"), and "ment" is also a noun - forming suffix (e.g., "achievement"), so they don't fit to form the required adjective.

Answer:

able (to form the word "achievable" which means "possible to be done successfully")