Line of sight on a grid: who can see/reach whom along rows, columns, diagonals

CAT has tested this idea 12 times across 3 papers, from 2017 to 2019. Solve one, and the others are the same method with different numbers or wording, which is why repeated concepts are the most efficient thing to practise.

Question	What it asks	Answer
CAT 2019 Slot 1 · DILR Q5	Street map intersections; people see along straight lines	C
CAT 2019 Slot 1 · DILR Q6	Street map intersections; people see along straight lines	B
CAT 2019 Slot 1 · DILR Q7	Street map intersections; people see along straight lines	B
CAT 2019 Slot 1 · DILR Q8	Street map intersections; people see along straight lines	D
CAT 2017 Slot 2 · DILR Q5	Queen on chessboard attacks unless a piece blocks the path	C
CAT 2017 Slot 2 · DILR Q6	Queen on chessboard attacks unless a piece blocks the path	D
CAT 2017 Slot 2 · DILR Q7	Queen on chessboard attacks unless a piece blocks the path	C
CAT 2017 Slot 2 · DILR Q8	Queen on chessboard attacks unless a piece blocks the path	C
CAT 2017 Slot 1 · DILR Q25	5x5 platforms of heights; reach along row/column if unblocked	C
CAT 2017 Slot 1 · DILR Q26	5x5 platforms of heights; reach along row/column if unblocked	D
CAT 2017 Slot 1 · DILR Q27	5x5 platforms of heights; reach along row/column if unblocked	C
CAT 2017 Slot 1 · DILR Q28	5x5 platforms of heights; reach along row/column if unblocked	C

Part of Grids & Matrices (67 questions since 2017).