Final answer:
The expression '18xyz' has the least number of terms, with just one term. Other given expressions contain more than one term, indicated by the presence of addition or subtraction signs.
Step-by-step explanation:
The question asks which expression has the least number of terms. An expression's terms are the elements that are added or subtracted. Looking at the given expressions:
- 2 + x
- 18xyz
- x + y - z
- Tyz - 3
Expression 2 (18xyz) consists of a single term. The other expressions all contain more than one term. When examining mathematical expressions, the least number of terms means the smallest count of separate entities connected by addition or subtraction. In this case, 18xyz is the expression with the least number of terms.