What's wrong with 'Bananas are unable to grow in cold countries'?
I may be drastically over-thinking this but, because the sentence (IMHO) seems to be grammatically acceptable, the problem must be one of semantics, if so then the issues would be:
1. Is the sentence unacceptable because it is semantically imprecise and therefore ambiguous?
What does “cold” mean in this sentence? Cold (adjective): 1) of or at a low or relatively low temperature, especially when compared with the human body low temperature, Cold (noun): 1) A low temperature; the absence of heat, especially in the atmosphere; cold weather; a cold environment.
What is meant by “countries” in this sentence? Countries (pl of country) noun: 1) A nation with its own government, occupying a particular territory; 2 (often the country) Districts and small settlements outside large towns, cities, or the capital; 3) An area or region with regard to its physical features (climate, terrain; geology, etc.). Definitions from Oxford Dictionaries online
2. Is the question semantically inadequate because not all bananas lack the ability, or are unable, to grow or to be successfully cultivated in cold countries?
Bananas in the Musa genus are native to Southeast Asia, and grow well in tropical and subtropical climates. Several varieties that evolved in higher elevations will survive colder climates, though few varieties will grow well in the cold. From SFGate.com.
3. Are the premises of the question erroneous? Is it wrong to confer the ability to grow upon a banana plant? Or does that ability more properly belong to human cultivators alone?
Able (adjective): 1) [with infinitive] having the power, skill, means, or opportunity to do something noun (plural abilities). Unable (adjective) [with infinitive] Lacking the skill, means, or opportunity to do something. Definitions from Oxford Dictionaries online.
At this point, from my perspective, the issue becomes philosophical rather than grammatical or semantic. As a layman I believe that plants do possess some degree of teleological capacity, but I understand that the conventional or orthodox scientific answer would be that teleology cannot be imputed to plants (banana or otherwise) and therefore a plant cannot be said to possess ability.
After considering each of the above possibilities I will hazard a (slightly) educated guess: the sentence is wrong because banana plants lack the ability to grow in cold countries independent of human cultivation.