1 to understand

2 to realize

3 to find out

1 tell-tale

2 informer (esp. to police)

3 whistleblower

4 grass

1 base (of operations)

2 industrial or military base

3 al-Qaeda

1 basic

2 fundamental

3 main

4 elementary

1 base

2 foundation

3 basis

4 underlying

5 classifier: 个 gè

1 lit. to know one and understand half (idiom); a smattering of knowledge

2 dilettante

3 amateur

1 lit. not requiring a detailed understanding (idiom); only looking for an overview

2 not bothered with the details

3 superficial

4 content with shallow understanding

1 to be good at understanding others (idiom)

1 to be at a loss (idiom)

1 inextricably linked (idiom)

2 inseparable