1 to be connected

2 traffic

3 transportation

4 communications

5 liaison

1 Russia

1 cartoon (loanword)

1 surname Gu

1 ancient times

2 olden times

1 a single slip may cause everlasting sorrow (idiom)

1 lit. doesn't (even) enter a single aperture (of one's head)

2 I don't understand a word (idiom)

3 it's all Greek to me

1 grasp this fundamental point and all the rest will follow (idiom)

1 to act in collusion (idiom)

1 mutual exchange of assistance (idiom)

2 to benefit from each other's strengths and make up each other's shortfalls

3 to reciprocate with material assistance

4 scratch each other's back