Shaded and unshaded squares are arranged in rows so that:

- the first row consists of one unshaded square,
- each row begins with an unshaded square,
- the squares in each row alternate between unshaded and shaded, and

![](https://cdn.mathpix.com/cropped/2024_04_20_e85ef69091c57cb633f3g-021.jpg?height=261&width=422&top_left_y=257&top_left_x=1315)

- each row after the first has two more squares than the previous row.

The first 4 rows are shown. The number of shaded squares in the 2020th row is
(A) 2022
(B) 2021
(C) 2020
(D) 2019
(E) 2018
The 1 st row has 0 shaded squares and 1 unshaded square.

The 2nd row has 1 shaded square and 2 unshaded squares.

The 3rd row has 2 shaded squares and 3 unshaded squares.

The 4 th row has 3 shaded squares and 4 unshaded squares.

Because each row has 2 more squares than the previous row and the squares in each row alternate betweeen unshaded and shaded, then each row has exactly 1 more shaded square than the previous row.

This means that, moving from the 4th row to the 2020th row, a total of $2020-4=2016$ additional shaded squares are added.

Thus, the 2020th row has $3+2016=2019$ shaded squares.

ANSWER: (D)