2. unleash   verb   

原句: Not to mention that video games unleash almost double the levels of dopamine experienced by humans at rest.

意思: to suddenly let a strong force, emotion, etc. be felt or have an effect 

例句: The government's proposals unleashed a storm of protest in the press.



3. therein   adverb   

原句: Therein lies the danger.

意思: in the place, object, document, etc. mentioned 

例句: The insurance policy covers the building and any fixtures contained therein.



4. susceptible   adjective   

原句: We humans are pretty susceptible to addictive tricks.

意思: very likely to be influenced, harmed or affected by sb/sth

字源: early 17th cent.: from late Latin susceptibilis, from Latin suscipere ‘take up, sustain’, from sub- ‘from below’ + capere ‘take’. 

例句: He's highly susceptible to flattery.



5. addictive   adjective   

原句: We humans are pretty susceptible to addictive tricks.

意思:
a. if a drug is  addictive , it makes people unable to stop taking it
b. if an activity or type of behaviour is  addictive , people need to do it as often as possible because they enjoy it 

例句:
a. Heroin is highly addictive.
b. I find jogging very addictive.