I didn't know that whales can sing 并列题名：I didn't know that whales can sing I didn't know that chimps use tools I didn't know that dinosaurs laid eggs I didn't know what time it was 并列题名：I didn't know that chimps use tools I didn't know that some birds hang upside down 并列题名：I didn't know that dinosaurs laid eggs I didn't know that crocodiles yawn to keep cool I wonder why whales sing