  Current studies in extractive question answering (EQA) have modeled the
single-span extraction setting, where a single answer span is a label to
predict for a given question-passage pair. This setting is natural for general
domain EQA as the majority of the questions in the general domain can be
answered with a single span. Following general domain EQA models, current
biomedical EQA (BioEQA) models utilize the single-span extraction setting with
post-processing steps. In this article, we investigate the question
distribution across the general and biomedical domains and discover biomedical
questions are more likely to require list-type answers (multiple answers) than
factoid-type answers (single answer). This necessitates the models capable of
producing multiple answers for a question. Based on this preliminary study, we
propose a sequence tagging approach for BioEQA, which is a multi-span
extraction setting. Our approach directly tackles questions with a variable
number of phrases as their answer and can learn to decide the number of answers
for a question from training data. Our experimental results on the BioASQ 7b
and 8b list-type questions outperformed the best-performing existing models
without requiring post-processing steps. Source codes and resources are freely
available for download at https://github.com/dmis-lab/SeqTagQA
