Why is holden nervous at the end of chapter 4

explanation:

the goblins and dwarves have different perspectives of things. bilbo is a hobbit and goblins dwarves and hobbits all believe and do a different way of living

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

you need to make an explanation. so, since you did not include one, so no one, and i mean no one can unfortunately you,