Task: Question Answering
Input (English): According to the endosymbiotic theory, double-membrane mitochondria originated as a result of some larger eukaryotic cells with flexible membranes engulfing smaller prokaryotic cells. Which of these explains where the outer layer of the double membrane of the mitochondria originated?  
 (A) the plasma membrane of the eukaryotic host (B) the nuclear membrane of the eukaryotic host (C) the ribosomes of the engulfed prokaryotic cell (D) the lysosomes of the engulfed prokaryotic cell
Output (English): A