Sure! Here are the sentences with unnecessary articles crossed out:

1. ~~The~~ Ancient Egyptians worshipped ~~the~~ Sun.
2. What did you have for ~~a~~ breakfast this morning?
3. The lion dance is called *shishi-mai* in ~~the~~ Japanese.
4. People perform ~~a~~ lion dance to bring ~~a~~ good luck.
5. ~~The~~ first, there is ~~a~~ special boat race.
6. The village festivals help us maintain our ~~the~~ traditions.
7. You shouldn’t refuse ~~a~~ young rice when the elderly offer it to you.
8. There are ~~the~~ lantern contests at the Ok Om Bok Festival.
9. It’s becoming ~~a~~ custom for many families in ~~the~~ Viet Nam to celebrate Women’s Day and ~~the~~ Family Day.
10. Dragon-snake *(Rong ran len may)* is a traditional Vietnamese game for ~~the~~ children.

Now let's complete the sentences with suitable prepositions:

1. Vietnamese people lay flowers or sometimes fruits **on** the altar for the belief that their ancestors will enjoy them.
2. We are going to prepare five-coloured sticky rice served **with** grilled chicken **for** the celebration.
3. A tradition is something special that is passed **down** through the generations.
4. You should find more information **about** a custom or a tradition in your hometown.
5. It’s a tradition **for** children to wake up early **on** Christmas Day.
6. Children usually wish longevity **for** their grandparents and parents.
7. Thai people throw water **on** one another as part of the cleansing ritual to welcome the Songkran New Year.
8. We broke **with** family tradition **by** travelling to New Zealand last Tet holiday.
9. Traditionally, children in the U.S. go from house to house to ask **for** sweets **on** Halloween.
10. We have a tradition **of** holding a family reunion **on** the first day of Tet.