Which are features of heroic couplets? select all that apply.
each couplet expresses a complete thought.
each couplet has a unique rhythm or meter.
the couplets are written in iambic pentameter.
the last word in the two lines that make up the couplet rhyme.

Features of heroic couplets are :

Each couplet expresses a complete thought.

The couplets are written in iambic pentameter.

The last word in the two lines that make up the couplet rhyme.

Explanation:

In a poem, two lines that comes next to each other right away is called as a couplet. Without one the complete meaning of the sentence will not be obtained. The meaning of the two lines will be similar to how they are closer to each other physically. All couplets are the two consecutive lines but not all pairs of consecutive lines forms a couplet.  The main condition to be a couplet is that they must be united and completed in nature.  

Heroic couplet has some unique features that makes it differ from regular couplet. They are rhymed and  always written in iambic pentameter.  The rhyme is attained by the last words of each line respectively. They have a thought that is complete when they are together.

i'm sure the answer you are looking for would be

a. an ice age

hope this contact me if this didn't or you need with more answers : )