The most appropriate option to fill in the blank is trivial.

The sentence "They wasted all the money on purchase of some trivial items" means that they spent a lot of money on things that were not important or valuable. The word "trivial" is the most appropriate word to use in the blank because it accurately reflects the fact that the items that they bought were not important or valuable.

The other options are not as appropriate.

• The word "important" is used to talk about things that are necessary or significant. This does not make sense in the context of the sentence, as the items that they bought were not necessary or significant.
• The word "significant" is also used to talk about things that are important or meaningful. This does not make sense in the context of the sentence, as the items that they bought were not important or meaningful.
• The word "quality" is used to talk about things that are good or high-quality. This does not make sense in the context of the sentence, as the items that they bought were not good or high-quality.