Final answer:
The correct word to complete the sentence is 'dwindle'. 'Dwindle' means to gradually reduce in size, amount, or intensity. It is the most appropriate word in this context.
Step-by-step explanation:
The correct word to complete the sentence is dwindle.
'Dwindle' means to gradually reduce in size, amount, or intensity. In the context of the sentence, it suggests that the person's investments will gradually decrease in value until they amount to nothing in a few months. For example, if someone invests in stocks that consistently lose value, their investments will dwindle over time.
Decrease, abate, and diminish are all synonyms of 'dwindle' and could be used interchangeably in the sentence. However, 'dwindle' is the most commonly used and appropriate word in this context.