Teacher:In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Teacher: Now, understand the problem? Solve this instance: (CNN) Your "BPA-free" plastic product may be no safer than the product it replaced, says a new UCLA study that analyzed the impact of a common BPA alternative on zebra fish embryos. The study joins a small but growing group of similar research sounding the alarm about so called "BPA-free" alternatives. "Our findings are frightening and important," said senior author and reproductive endocrinologist Nancy Wayne. "Consider it the aquatic version of the canary in the coal mine." After decades of animal research linked BPA (Bisphenol A), a known endocrine disruptor, to problems with brain and reproductive development, early puberty and a rise in breast and prostate cancer, many manufacturers stopped using the chemical to harden plastics, replacing it with "BPA-free" alternatives. The most common replacement is BPS (Bisphenol S), said Wayne.BPA-free alternatives may be no safer than BPA, say researchersMost common alternative, BPS, linked in study to disruptions of estrogen and thyroid hormones 
 Question:"In the presence of either _ or BPS, embryonic development was accelerated.
Student:
BPA