Pretty straightforward. Although, the correct option might be a bit iffy (considers necessary condition as a sufficient one), but elimination leaves with only one option.:
A Language is the only major obstacle blocking Leviathan from entering emerging markets.
Keep As can be seen from the passage, this is clearly the intention behind hiring multilingual candidates, so that company grows market in geographies where English is not the first language.
B Other companies have successfully implemented this strategy in recent years.
Eliminated Success of other companies is irrelevant to the subject company (There may be various factors affecting the market expansion), hence this could not have been the assumption for conclusion.
C Many American employees would resist being transferred to emerging markets.
Eliminated This is completely out of context. further, there might be no need to transfer employees at all, it may be a BPO type company requiring only internet/telephonic interaction with customers.
D Leviathan would have to provide language courses to its employees to prevent their language skills from becoming atrophied.
Eliminated This has not been assumed, as no training related conclusions have been made.
E Leviathan would pay for the cost of transferring American employees to developing countries.
Eliminated This is completely out of context. further, there might be no need to transfer employees at all, it may be a BPO type company requiring only internet/telephonic interaction with customers.