p开头的单词用a还是an

　　The panda is a shy creature.

　　熊猫是一种胆小的.动物。

　　It is well known that bamboo shoots are a panda's staple diet.

　　竹笋是熊猫的主要食物，这是人所共知的。

　　Pea pods burst open when overripe.

　　豌豆过熟就会爆裂。

　　Study on the Preparation, Characteristic and Application of Pea Protein Isolate

　　豌豆分离蛋白的制备、性质及应用研究

　　Only a real princess could feel one little pea!

　　只有真正的公主才能感觉到一个小豌豆！