Which of the following is **TRUE** about subsets of the real numbers?
A$\mathbb{N} \subset \mathbb{Z} \subset \mathbb{Q} \subset \mathbb{R}$
B$\mathbb{Q} \subset \mathbb{Z} \subset \mathbb{N}$
C$\mathbb{R} \subset \mathbb{Q}$
DThe set of irrational numbers $\mathbb{T}$ is a subset of $\mathbb{Q}$
Answer & Solution
Correct answer: A. $\mathbb{N} \subset \mathbb{Z} \subset \mathbb{Q} \subset \mathbb{R}$
Each containment $\mathbb{N} \subset \mathbb{Z}$ (add zero and negatives), $\mathbb{Z} \subset \mathbb{Q}$ (each integer = $n/1$), $\mathbb{Q} \subset \mathbb{R}$ (rationals are real). The chain holds.
- **B** reverses the containments.
- **C** is false; $\sqrt{2} \in \mathbb{R}$ but $\sqrt{2} \notin \mathbb{Q}$.
- **D** is false; $\mathbb{T}$ and $\mathbb{Q}$ are disjoint.
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