**Answer:**

Relational algebra is a formal query language used to retrieve data from relational databases. It consists of a set of operations that can be applied to relations (tables) to produce a desired result. However, there are certain features that go beyond the capabilities of relational algebra. These features include aggregate computation, multiplication, and finding transitive closure. Let's discuss each of these features in detail:

**1. Aggregate computation:**
Aggregate functions are used to perform calculations on a set of values and return a single value as the result. Examples of aggregate functions include SUM, COUNT, AVG, MIN, and MAX. These functions are used to compute totals, averages, counts, and other statistical calculations.

Relational algebra does not have built-in operators to perform aggregate computations. While it is possible to manually compute aggregates using basic relational algebra operations such as selection, projection, and join, it is not an efficient or convenient way to perform such calculations. Therefore, aggregate computations are beyond the capability of relational algebra.

**2. Multiplication:**
Multiplication in the context of relational algebra refers to the Cartesian product operation, which combines every tuple from one relation with every tuple from another relation. The result is a new relation that contains all possible combinations of tuples from the two input relations.

While relational algebra does provide the Cartesian product operation, it does not have a built-in operator for multiplication that can perform multiplication of values within a relation. In other words, relational algebra cannot perform mathematical multiplication on individual attribute values. Therefore, multiplication is beyond the capability of relational algebra.

**3. Finding transitive closure:**
Transitive closure is a concept in graph theory that involves finding the complete set of all possible paths between nodes in a directed graph. In the context of relational algebra, finding the transitive closure involves determining the set of all tuples that are indirectly related through a series of intermediate tuples.

Relational algebra does not have a built-in operator to find transitive closure. While it is possible to manually compute the transitive closure using recursive queries or iterative algorithms, it is not a native operation of relational algebra. Therefore, finding transitive closure is beyond the capability of relational algebra.

Based on the above explanations, it is clear that all of the desired features mentioned in the options (aggregate computation, multiplication, and finding transitive closure) are indeed beyond the capability of relational algebra. Therefore, the correct answer is option 'D'.