Unit 1 · TENSES

Present continuous

I am doing

Unit 2 · TENSES

Present simple

I do

Unit 3 · TENSES

Present continuous and present simple 1

I am doing and I do

Unit 4 · TENSES

Present continuous and present simple 2

I am doing and I do

Unit 5 · TENSES

Past simple

I did

Unit 6 · TENSES

Past continuous

I was doing

Unit 17 · VERBS

Have and have got

Unit 18 · VERBS

Used to (do)

Unit 71 · NOUNS

Countable nouns with a/an and some

Unit 72 · NOUNS

A/an and the

Unit 85 · NOUNS

Some and any