Dear Grandma and Grandpa,

    I miss you so much. Thank you for the new bike! I'm so excited! How did you know 1 is my favorite color?

    When I first 2 the box under the Christmas tree, I didn't know what it was. I thought it was 3 small to hold a bike. Then when I opened it, I saw that the bike was in small pieces. That's 4 the box was small!

    Dad and I put them 5 the next day. It was a lot of fun. 6 we finished, I got on the blue bike and 7 around the town. My old bike was too small for me. This one is just 8. It looks great, too! All 9 friends want one like this now. Dad said that I could take my 10 when we go to visit you in the spring. I can't wait.

Yours,

David

— Are those shoes yours?

— No, they aren't.

— Whose shoes are they,         ?

— They are Tom's.

资料表明：将皮肤晒黑甚至晒伤的罪魁祸首是太阳光中的长波紫外线．雄鹰物理实验小组在老师的协助下通过检测若干衣服的防晒效果，为爱美人士提供选择防晒衣服的科学依据．检测方法：先用光纤探头和计算机测算出阳光中长波紫外线的强度；再把衣服挡在光纤探头上，测算出透射到光纤探头上的长波紫外线强度．利用前后两次测得的长波紫外线的强度计算出长波紫外线的透过率．实验数据如下表所示：

分析表中数据，回答下列问题：

（1）该实验验证衣服的防晒效果好坏是通过____ 比较．

（2）条件相同时，比较实验　____ 　得到的结论是衣服层数越多，防晒效果越好．

（3）根据测量结果，请向你的朋友提出一条夏季户外活动时着装的建议．____ 

调查某豌豆种群中一对相对性状（甲、乙性状）的频率，发现甲性状占50%，其余均为乙性状。若分别取足够多数量的甲、乙两种性状的个体分别自交，发现50%乙性状的子代产生甲性状，而甲性状的子代未发现乙性状。以下结论错误的是