（2015•垫江县）将干燥的小麦种子放在酒精灯上燃烧，最后剩下的灰白色物质是（ ）

下列各句中没有语病的一句是（    ）

    When I spent the summer with my grandmother, she always set me down to the general store with a list. Behind the counter was a lady like no one I'd ever seen.

    “Excuse me,” I said. She looked up and said, “I'm Miss Bee.”

    “I need to get these.” I said, holding up my list. “So? Go get them. ” Miss Bee pointed to a sign. “There's no one here except you and me and I'm not your servant, so get yourself a basket from that pile.”

    I visited Miss Bee twice a week that summer. Sometimes she shortcharged me. Other times she overcharged. Going to the store was like going into battle. All summer long she found ways to trick me. No sooner had I learned how to pronounce “bicarbonate of soda” and memorized its location on the shelves than she made me hunt for it all over again. But by summer's end the shopping trip that had once taken me an hour was done in 15 minutes.

    “All right, little girl,” she said. “What did you learn this summer?” “That you're a meanie!” I replied. Miss Bee just laughed and said, “I know what you think of me. Well, I don't care! My job is to teach every child I meet life lessons. When you get older you'll be glad!” Glad I met Miss Bee? Ha! The idea was absurd…

    Until one day my daughter came to me with homework troubles. “It's too hard,” she said. “Could you finish my math problems for me?”

    “If I do it for you, how will you ever learn to do it yourself?” I said. Suddenly, I was back at that general store where I had learned the hard way to add up my bill by myself. Had I ever been overcharged since?

苔藓植物、蕨类植物也能形成种子．　

同学们为了探究食物保鲜的方法，用煮沸灭菌并冷却的肉汤设计了如图所示的对照实验．根据图示判断他们欲探究的问题是（    ）