The correct answer is (D) distinct.

Here is a breakdown of why this word works best:

The sentence states that before Walt Whitman, there was no $\qquad$ American voice in poetry. The second half of the sentence provides a reason for this: Emerson's poems, while esteemed, were not "altogether different from that of England's Lake Poets."

This means that American poetry before Whitman lacked a unique or characteristic style of its own.
- (D) distinct: This word means recognizably different in nature from something else of a similar type. It perfectly captures the idea that American poetry before Whitman was not separate or unique from its English influences.

Let's look at why the other options are incorrect:
- (A) influential: While a voice might be influential, the sentence's focus is on the lack of a unique American identity, not its influence.
- (B) celebrated: The sentence mentions that Emerson's poems are "highly esteemed," so a lack of celebration isn't the issue.
- (C) solitary: The sentence is not about a lack of a single poet, but a lack of a unique poetic style.
- (E) general: This is the opposite of the intended meaning. A general voice is what they had; they lacked a specific, unique one.