It - (as a mandatory subject)

Is raining a lot today.

It's raining a lot today.

It will be our anniversary next Tuesday.

Will be our anniversary next Tuesday.

Is my birthday.

It's my birthday.

Is her dog, not mine.

It's her dog, not mine.

It's a really nice day.

Is a really nice day.

I really like this work of art. Is so beautiful.

I really like this work of art. It's so beautiful.

Is important to drink lots of water every day.

It's important to drink lots of water every day.

It was good to hear from you.

Was good to hear from you.

How was your week? It was good, and yours?

How was your week? Was good, and yours?

Is my ambition to run a three hour marathon.

It's my ambition to run a three-hour marathon.