The prefix "semi-" can have several meanings, such as "half in value" or "happening once halfway through a specific time period." In this context, we are focusing on "happening once halfway through a specific time period."
Given the sentence: "The women's club held fundraisers on a semiannual basis." Here, the specific time period is a year.
If something happens semiannually, it occurs halfway through the year and again at the end of the year. Thus, semiannual means "happening twice a year."
So, based on the definition of the prefix "semi-" and the context provided, the correct interpretation is:
twice a year.
