The preposition 凭
The preposition 凭 
is used to explain certain things. The nouns following 凭 can be something concrete or something abstract (such as truth, knowledge or feelings).
is used to explain certain things. The nouns following 凭 can be something concrete or something abstract (such as truth, knowledge or feelings).Examples
凭你的知识，通过这次面试是很容易的
It'll be easy to pass this interview with your knowledge
píng nǐ de zhīshi, tōngguò zhè cì miànshì shì hěn róngyì de
你可以凭学生证在博物馆享受折扣优待
You can enjoy a special discount at the museum with your student ID card
nǐ kěyǐ píng xuéshengzhèng zài bówùguǎn xiǎngshòu zhékòu yōudài
凭 is often used with 什么 to indicate dissatisfaction or anger: "On what basis do you...?".
to indicate dissatisfaction or anger: "On what basis do you...?".Examples
她凭什么指责我？
Why is she accusing me?
tā píng shénme zhǐzé wǒ
我不是得了四分吗，凭什么骂我？
Didn't I get a "B"? Why are you scolding me?
wǒ bú shì dé le sì fēn ma, píng shénme mà wǒ