Step 1: Idea:
Recall the classical decomposition of a time series and count the parts.
Step 2: Write the model.
The value at time $t$ is built from $T_t$ (trend), $S_t$ (seasonal), $C_t$ (cyclical) and $I_t$ (irregular). For example, in the multiplicative model: \[ Y_t = T_t \times S_t \times C_t \times I_t \]
Step 3: Match each statement.
A is $S_t$, B is $T_t$, C is $I_t$ and D is $C_t$. Every statement names one of the four terms.
Step 4: Rule out shorter lists.
If we drop any term, the model cannot explain all patterns. For example, without $S_t$ we cannot explain repeating yearly peaks, and without $C_t$ we cannot explain multi-year booms and slumps.
Step 5: Select the option.
The list that has all four is A, B, C and D, which is option 4.
Final Answer:
All four components shape a time series.
\[ \boxed{\text{A, B, C and D}} \]