Question

I ... who it was Didn't know Know Not know Didn't knew

Answer 1

Скорее всего
I know

Answer 2

When expressing negation in the past simple tense, the correct form is "didn't know" [[2]](https://brilliantatenglish.com/do-we-say-didnt-know-or-didnt-knew/). The word "didn't" is used with the base form of the verb, in this case, "know" [[2]](https://brilliantatenglish.com/do-we-say-didnt-know-or-didnt-knew/). Here are some example sentences to illustrate this:

1. "I didn't know who it was."2. "They didn't know how to use the new software."3. "She doesn't know that smoking is bad for her health." [[1]](https://www.tprteaching.com/didnt-knew-didnt-know/) 4. "We didn't know she was married."5. "I didn't know how to fix my computer, so I gave it to the repair shop."6. "He doesn't know which job he wants to apply for." [[1]](https://www.tprteaching.com/didnt-knew-didnt-know/) 7. "They didn't know how to respond to that situation."8. "I don't know what is happening." [[1]](https://www.tprteaching.com/didnt-knew-didnt-know/)

In all these sentences, "didn't know" is the correct form to use when expressing negation in the past simple tense