1.Rita is writing a story.

2.I was buying vegetables.
3.seema was eating apples.
4. The family was watching a cricket match.

All four are in active voice. That is, the subject is doing the action.

http://www.chompchomp.com/terms/actionverb.htm

Now you need to turn each sentence around and convert the verb to passive voice. ~~> The subject will NOT be doing the action of the verb.
http://www.englishclub.com/grammar/verbs-voice-passive.htm

I'll do the first one; then you do the rest, and I'll check your work.

Rita is writing a story.
A story is being written by Rita.

Vna

Vhuii

Based on the given information, here are the step-by-step descriptions of each activity:

1. Rita is writing a story.
- Rita has a pen and paper or is using a digital device to write the story.
- She might be sitting at a desk or in a comfortable spot where she can concentrate.
- She begins by thinking about the plot, characters, and setting of the story.
- Then, she starts putting her thoughts into words, crafting sentences to create a narrative.
- She may take breaks occasionally to think or edit her work, before continuing to write.

2. I was buying vegetables.
- The person speaking is in a location where vegetables are being sold, like a grocery store or market.
- They are likely carrying a shopping bag or basket to hold the vegetables they intend to buy.
- They walk through the aisles, examining different types of vegetables and selecting the ones they need.
- They might check for freshness, use their senses to assess quality, and compare prices before making a decision.
- Finally, they make their way to the cashier to pay for the vegetables and then leave the store.

3. Seema was eating apples.
- Seema has one or more apples in her possession.
- She may be sitting at a table, on a couch, or simply holding the apple in her hand.
- Seema takes a bite out of the apple, tasting its flavor and experiencing its texture.
- She chews and swallows the apple, possibly savoring the taste or enjoying the act of eating.
- Depending on her preference, Seema might eat the entire apple or consume only a portion of it.

4. The family was watching a cricket match.
- The entire family is gathered in a living room, sports bar, or any other place where the match is being broadcast.
- They could be sitting on a couch, chairs, or even on the floor, arranged to have a clear view of the TV screen.
- They turn on the TV and navigate to the channel broadcasting the cricket match.
- As the match progresses, the family members are focused on the screen, watching the players and their actions.
- They may cheer, clap, or show excitement when something exciting or significant happens in the match.

The given sentences are examples of past continuous tense, which is used to describe an ongoing action that happened in the past.

To form the past continuous tense, we use the past tense of the helping verb "to be" (was/were) followed by the present participle form of the main verb (ends with -ing).

1. Rita is writing a story.
To change this sentence to past continuous tense, we use "was" (past tense of "to be") followed by "writing" (present participle form of "write").
Past continuous tense: Rita was writing a story.

2. I was buying vegetables.
In this sentence, we already have the correct form of past continuous tense. It is formed using "was" (past tense of "to be") followed by "buying" (present participle form of "buy").

3. Seema was eating apples.
Similar to the previous sentences, we use "was" (past tense of "to be") followed by "eating" (present participle form of "eat").
Past continuous tense: Seema was eating apples.

4. The family was watching a cricket match.
Again, we use "was" (past tense of "to be") followed by "watching" (present participle form of "watch").
Past continuous tense: The family was watching a cricket match.

So, the correct sentences in past continuous tense are:
1. Rita was writing a story.
2. I was buying vegetables.
3. Seema was eating apples.
4. The family was watching a cricket match.