Read this excerpt from "The Birches" by Robert Frost. Which line shows enjambment?

I'd like to go by climbing a birch tree,

And climb black branches up a snow-white trunk

Toward heaven, till the tree could bear no more,

But dipped its top and set me down again.

That would be good both going and coming back.

One could do worse than be a swinger of birches.

Answer choices are lines 3-6

Toward heaven, till the tree could bear no more,

Explanation:

In poetry, the term enjambment refers to the continuation of a sentence without a pause beyond the end of a line. In other words, the sentence doesn't end at the end of the verse but rather continues in the next one.

In this example, we see that in line number 2 "And climb black branches up a snow-white trunk" the sentence continues in line number 3 (as the complete sentence would be "and climb black branches up a snow-white trunk towards heaven")

Therefore, we can see that the enjambment is present in line number 3 "Toward heaven, till the tree could bear no more"

We can see that lines 4 to 6 (the other answer choices) are complete sentences by themselves so therefore, the correct answer is line number 3.