file name :常见中老年疾病的防治
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Payment Method:
1、Open Tittle
2、Click to Pay New
3、Click on the material you want to buy
4、Click on "Payment Methods"
5、Click on the material you want to buy
6、Choose from one of your existing payment methods or add a new one
7、Complete purchase
NOTE: If you add a payment method when making a purchase, it will be saved in your account.