Task: Question Answering
Input (English): Background Paragraph: You may hear males "ribbiting," producing a mating call used to attract females to the bodies of water best for mating and breeding. Frog calls can occur during the day or night. Each frog species has a different call that is used to attract mates and warn off rivals. When a female picks a male whose call she likes, the male grabs her and squeezes across her back and around her abdomen. This causes the female to release her eggs. The male then fertilizes the eggs and, in some species, also guards them. 
Story: Sandra liked all creatures but loved to study frogs. Her sister Julie studied more about fish and butterflies. They both loved nature. 
Question: Which sister learned more about different calls used by different species of frogs?
Output (English): Sandra.