Dia tidak menentang keputusan itu.

Because tidak is the normal negator for verbs and adjectives, while bukan is mainly used to negate nouns or to correct/contrast something.

Here, menentang is a verb meaning to oppose, so tidak is the correct choice:

• Dia tidak menentang... = He/She does not oppose...

Compare:

• Dia bukan guru. = He/She is not a teacher.
  Here guru is a noun, so bukan is used.

Menentang means to oppose, to be against, or to resist something.

In this sentence, it means the person is not against the decision.

Be careful not to confuse menentang with tentang meaning about/regarding. They look similar, but they are different words in use.

In Malay, demonstratives like ini (this) and itu (that) usually come after the noun:

• keputusan itu = that decision
• rumah ini = this house

This is different from English, where this/that comes before the noun.

Literally, keputusan itu means that decision. But in real usage, it can sometimes feel close to the decision, especially when the decision is already known from context.

Malay does not have a direct article system like English the and a/an, so words like itu often help make a noun more definite or specific.

You usually know from context, because Malay verbs do not change form for tense the way English verbs do.

So Dia tidak menentang keputusan itu could mean:

• He/She does not oppose that decision
• He/She did not oppose that decision
• He/She is not opposing that decision

If the speaker wants to make the time clearer, they can add time words such as:

• semalam = yesterday
• sekarang = now
• esok = tomorrow

Keputusan comes from the root putus, which is related to the idea of deciding or being settled/finalized. The pattern ke-...-an often forms nouns.

So:

• putus = decide / final / broken off, depending on context
• keputusan = decision, result, outcome

In this sentence, keputusan means decision.

Yes, it is quite similar:

• Dia = subject
• tidak = negation
• menentang = verb
• keputusan itu = object

So the structure is basically:

Subject + not + verb + object

That makes this sentence fairly straightforward for English speakers.

Yes. That is a common informal version.

• tak = informal spoken form of tidak
• tu = informal spoken form of itu

So:

• Dia tidak menentang keputusan itu. = neutral/formal
• Dia tak menentang keputusan tu. = informal/spoken

Both mean the same thing.

Sometimes in conversation, yes—if the subject is already obvious from context. For example, someone might just say:

• Tidak menentang keputusan itu.

But as a full, clear sentence, especially for learners, Dia tidak menentang keputusan itu is the more complete form.

A simple approximate pronunciation is:

dee-ah tee-dahk muh-nuhn-tahng kuh-poo-too-sahn ee-too

Very roughly by word:

• Dia ≈ dee-ah
• tidak ≈ tee-dahk
• menentang ≈ muh-nuhn-tang
• keputusan ≈ kuh-poo-too-sahn
• itu ≈ ee-too

Pronunciation varies a bit by region and speaking speed, but this will get you close.