This is a sentence in the TOEFL test and it contains incorrect underlined word or group of words.

Most probably because of the likable rapport between anchors, the night newscast on the local ABC affiliate has recently moved well beyond its competitors in the ratings battle.

I really couldn't see anything wrong with it.

The term "most probably" seem to be incorrect but I didn't know how wrong it is. If it's true, could you show me the different between using "most probably" and "most probable" in this sentence.

The word "night" used in this sentence may be incorrect, because it is a noun. It seems proper to use the adjective "nightly" to describe the noun "newscast". But I think "night newscast" is all right.

Thanks !
In your sentence, the word "most" is synonymous with "very" and it functions as an adverb modifying the word "probably". Adverbs can be used to modify verbs, adjectives and also other adverbs. The combination "most probably" is grammatically OK. Look here:

The combination "most probable" would refer to a noun. For example: "the most probable reason"

In your sentence, I would choose to change the word "night" to "nightly".

Did this sentence actually come from an official TOEFL test? Or did it come from TOEFL preparation materials or a TOEFL preparation website?
I'd bet that they want you to change night to nightly, but likable rapport strikes me as pretty strange too.

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Hi Yankee,

Thank for your reply. Your explain about "most probably" and "most probable" was so clear.

You're right. This sentence come from a TOEFL preparation materials. That I said it come from a TOEFL test is just to emphasize the incorrect word must be wrong with TOEFL grammar (but it may be correct in speaking or informal english).

Could you explain to me more about "night" and "nightly".

I know that "nightly" is an adjective, so using it to describe the noun "newscast" is absolutely right.

But with the noun "shift", I'm sure that "night shift" is correct. Why can we use "night" with the noun "shift" ?

Moreover, in that sentence, if we write "day newscast" instead of "night newscast", are there any proper adjective in this situation?

Thanks !
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CalifJim but likable rapport strikes me as pretty strange too.
Me, too. A collocation such as "easy rapport" would sound more typical to me.
(That's why I asked whether it was actually a question from a real TOEFL test.)