Select the option that can be used as a one-word substitute for the given group of words.
"A woman having more than one husband at the same time"

Let's look at the meanings of the given words:
* Polyandry: The practice or condition of having more than one husband at the same time.
* Polymathy: Great or varied learning; the knowledge of a polymath.
* Monogamy: The practice of marrying or having a relationship with only one person at a time.
* Endogamy: The custom of marrying only within the limits of a local community, clan, or tribe.

Therefore, "Polyandry" is the correct one-word substitute.