1. Color the diagrams such as the triangle and square red.(Is this one correct grammatically?)

2. What is the suitable English term for the shelf where items are placed at a mart? (This is a question.)

3. Do you know how to memorize the colors of the rainbow? Would you like to let me know? (Question)

4. Match Picture one with a suitable picture.

4-2. You should match each picture with a sentence.

4-3. The picture is matched with the first sentence.

(Are the three sentences correct?)

1. Color the diagrams such as the triangle and square red.(Is this one correct grammatically?) Yes, it's correct. It would be better if you had a comma after "diagrams" and after "square."

2. What is the suitable English term for the shelf where items are placed at a mart? (This is a question.) They are referred to as grocery shelves or market shelves.

3. Do you know how to memorize the colors of the rainbow? Would you like to let me know? (Question) The easiest way I've found to remember those colors in order is this: ROY G BIV (like someone's name) -- it stands for red, orange, yellow, green, blue, indigo, violet. In fact, there's an art gallery in Palm Springs, California, that is called Roy G Biv!!

4. Match Picture one with a suitable picture.

4-2. You should match each picture with a sentence.

4-3. The picture is matched with the first sentence.

All the #4 sentences sound fine.

1. The sentence "Color the diagrams such as the triangle and square red" is grammatically correct. However, it could be rephrased for clarity as "Color the diagrams, such as the triangle and square, in red."

2. The suitable English term for the shelf where items are placed at a mart is "display shelf" or "retail shelf."

3. To memorize the colors of the rainbow, you can use the mnemonic device "ROYGBIV," which stands for Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Each letter represents a color in the rainbow. Alternatively, you can also remember the colors by visualizing a rainbow and practicing identifying each color.

4. "Match Picture one with a suitable picture" is a correct sentence.

4-2. "You should match each picture with a sentence" is a correct sentence.

4-3. "The picture is matched with the first sentence" is a correct sentence, but it may require more context to be fully understood.