How to make child img's dynamic width equal to the parent block with flex?

Question

css

Good afternoon!
The problem is in the title of the question.
The .b-block property is set to display: flex. When changing the width of the screen, it is necessary that the child img inside always be equal to the width of the parent - .b-block
Can this be done using css?
Link to Codepen

Answer 1

.b-main .b-block__item {
    list-style: none;
    width: 100%;
    flex-shrink: 0;
}

Answer 2

img {
  width: 100%;
}

doesn't fit?