口琴和口琴内部的金属片,短的金属片振动的频率_____,音调_____；长的金属片振动的频率_____,音调_____.

口琴的吹气用B表示,单词是“Blowing”,——表示向口琴里送气；
它的吸气用D表示,表示把口琴力度气排出——英语单词是“Deaeration”；
不知道这个解释,!

The harmonica is a free reed wind instrument which is played by blowing air into it or drawing air out by placing lips over individual holes (reed chambers) or multiple holes. The pressure caused by blowing or drawing air into the reed chambers causes a reed or multiple reeds to vibrate up and down creating sound. Each chamber has multiple, variable-tuned brass or bronze reeds which are secured at one end and loose on the other end, with the loose end vibrating and creating sound.
Reeds are pre-tuned to individual tones, and each tone is determined according to the size of reed. Longer reeds make deep, low sounds and short reeds make higher-pitched sounds. On certain types of harmonica the pre-tuned reed can be changed (bending a note) to another note by redirecting air flow into the chamber. There are many types of harmonicas, including diatonic, chromatic, tremolo, orchestral, and bass versions.
The harmonica is used in blues and American folk music, jazz, classical music, country music, rock and roll, and pop music. The harmonica has other nicknames, especially in blues music, including: "harp," "blues harp", "french harp", and "mouth organ."

2×3=6（种）．
答：一共有6种不同的选择方法．
故答案为：6．

点评：
本题考点： 乘法原理．

考点点评： 本题考查了乘法原理，即做一件事情，完成它需要分成n个步骤，做第一步有M1种不同的方法，做第二步有M2种不同的方法，…，做第n步有Mn种不同的方法，那么完成这件事就有M1×M2×…×Mn种不同的方法．

先天性行为是指动物生来就有的，由动物体内的遗传物质所决定的行为，称为先天性行为例如：蜜蜂采蜜，蚂蚁建巢，蜘蛛织网，鸟类迁徙等． 先天性行为是动物的一种本能行为，
不会丧失．后天性行为是动物出生后通过学习得来的行为．动物建立后天行为的主要方式是条件反射．参与神经中枢是大脑皮层不是与生俱来的而是动物在成长过程中，通过生活经验和
“学习”逐渐建立起来的新的行为．大象吹口琴、狗钻火圈、猴子钓鱼，是通过学习得来的行为，属于后天性行为；小狗吃奶，是生来就有的，不学就会的，由体内的遗传物质所决定的先天性行为．
故选：A．

点评：
本题考点： 动物的先天性行为和学习行为的区别．

考点点评： 解答此类题目的关键是理解动物行为获得的途径和特点．