I like to see it lap the Miles by Emily Dickinson

I like to see it lap the Miles—
And lick the Valleys up—
And stop to feed itself at Tanks—
And then—prodigious step

Around a Pile of Mountains—
And supercilious peer
In Shanties—by the sides of Roads—
And then a Quarry pare

To fit its sides
And crawl between
Complaining all the while
In horrid—hooting stanza—
Then chase itself down Hill—

And neigh like Boanerges[1]—
Then—prompter than a Star
Stop—docile and omnipotent
At its own stable door—

Throughout "I like to see it lap the Miles," Dickinson uses the metaphor of a horse to describe the train. Which three qualities are emphasized through the use of this metaphor?

1. beauty
2. endurance
3. humility
4. speed
5. strength
6. unpredictability