______ of that country _______ by snow.

现有一未受人类干扰的自然湖泊，某研究小组考察了该湖泊中处于食物链最高营养级的某鱼种群的年龄组成，结果如下表：

注：表中1+表示鱼的年龄大于1，小于2，其他以此类推．

回答下列问题：

（1）通常，种群的年龄结构大致可以分为三种类型，分别是____ ，研究表明：该鱼在3+时达到性成熟（进入成年），9+时丧失繁殖能力（进入老年），根据表中数据可知幼年、成年和老年3个年龄组个体数的比例为____ ，由此可推测该鱼种群数量的变化趋势是____ 

（2）如果要调查这一湖泊中该鱼的种群密度，常用的调查方法是标志重捕法．标志重捕法常用于调查____ 强、活动范围广的动物的种群密度．

（3）在该湖泊中，能量沿食物链流动时，所具有的两个特点是____

Dear Mr. Wang,

    Someone comes to the office to see you in the morning, but you and your wife are out. He comes here at 10am. Because he is very busy, he goes away half an hour later. He tells me that he is your classmate at college(大学). Now he teaches Chinese in a high school(高中) in this city and he lives near the No. 6 Middle School. He is a very tall man with short hair. He wears a pair of glasses. He tells me his telephone number is 33426685. He is often at home at 7:00 pm. So you can call him in the evening.

植物生长需要的养料是由植物绿色的叶依靠____提供的能量，利用____ 和____ 制成的。