1. Which is correct?

Nguyen Secret project
Or
Nguyen's Secret project

2. Which is correct?
She is five foot tall
Or she is five feet tall

The second choice for both.

Nguyen's Secret project

She is five feet tall.

1. The correct phrase is "Nguyen's Secret project."

To determine which phrase is correct, it's important to understand the concept of possessive nouns. In English, when we want to indicate that something belongs to someone, we use an apostrophe ('s) after the noun.

In this case, we are referring to a secret project that belongs to Nguyen. Therefore, the correct way to express this would be "Nguyen's Secret project." The apostrophe indicates possession, and it is placed after the name "Nguyen" to show that the project belongs to Nguyen.

2. The correct phrase is "She is five feet tall."

To determine the correct phrase, we need to consider the proper usage of measurement and quantity. In English, when we talk about someone's height, we typically use the plural form of the noun "foot" (feet), as well as the word "tall" to indicate height.

In this case, since we are referring to someone's height as measured in feet, the correct way to express it is "She is five feet tall." The plural form "feet" is used because it follows the numeral "five," and "tall" is used to specify the height measurement.