Continue sounds better in that sentence but note that that sentence does not represent idiomatic standard English. Instead it should be something such as continue in an angry manner. Or continue angrily. The use of the 'flat adverb' angry is okay but might not represent standard English. For example, If a conversation starts angrily, it will almost certainly ...
The correct one is continue.
The difference is subtle, but 'maintain' means:
cause or enable (a condition or state of affairs) to continue.
This is wrong because when the conversation starts angry, it is not causing it to continue angry. You'd say that the people having the angry conversation maintained it (without them, it wouldn't continue angry)
It's a bit confusing, since I can think of two ways to read this sentence:
"I heard a loud cheer from the tent in which the acrobats were performing. They were obviously quite thrilling to watch."
Who were thrilling to watch? The acrobats. To watch the acrobats was a thrilling experience.
"I asked my friends if they wanted to jump into the pool with me. ...
The reason that the first option is correct and the second isn't is that the phrase on the contrary always introduces an idea that cancels an implication that has been made in the previous discourse (by somebody, not necessarily the speaker).
In this particular case, if the government's actions were sporadic (happened infrequently at random intervals), that ...
The relevant definition of operation in Merriam-Webster's Eleventh Collegiate Dictionary (2003) doesn't mention cutting as a prerequisite:
operation n ... 4 : a procedure performed on a living body usu. with instruments esp. for the repair of damage or the restoration of health
Under the Eleventh Collegiate's definition, a bone marrow transplant would ...
They were obviously quite _____ to watch.
The adjectives thrilling and content are different types of adjective. In the OP's examples, these adjectives are complements of the verb BE.
Importantly, both of these types of adjective can be followed by infinitives.
thrilling to watch
content to watch
Notice that these ...
Very [few books] are read ___ [Harry Potter]; by children
The logical choice, in my opinion would be to use b) more than, than a) as much as.
My reasoning for this is that more is the irregular comparative of the base adjective much and since the base adjective few is already used, another base adjective can’t be used in the same sentence:
Very few ...
The reason that maintain is wrong is that maintain is a transitive verb: it must take an object, something which is maintained by a positive action.
Continue can be transitive, but it can also be intransitive. Something may simply continue; it doesn't have to be continued.
Thus the conversation continues.
The use of an adjective after continue rather than ...
The context of the linked text is that when reciprocation isn't expected, it is very much appreciated when it does occur, so it seems the author intended positive to convey the idea of emotionally uplifting. It's a bonus because it wasn't a calculated part of the exchange. Unfortunately, positive bonus ends up being redundant as @deadrat observes, so is a ...
It's an ambiguous question, and the right word depends on the point of view: is this describing the watchers or the watched?
If you're talking about how the watchers feel, you need "content," which describes how people feel. "Thrilling" means inducing excitement. The TV show is thrilling; the people are thrilled to watch it.
If you're talking about how ...
knowledge: facts, information, and skills acquired by a person through experience or education. Richard has knowledge about when the train leaves.
information: facts provided or learned about something or someone. Richard supplied information about when the train leaves.
The key factor is that information is provided, while knowledge is simply known. It ...