Which option correctly names both the largest living bird and the smallest living bird species?

Introduction / Context:
This question checks your general science knowledge about extremes in the animal kingdom, specifically birds. It asks you to identify both the largest living bird and the smallest living bird species in a single paired option. Such questions are very common in competitive examinations because they combine two factual points into one multiple-choice item, testing both memory and careful reading.

Given Data / Assumptions:

• We need to identify the largest living bird species by size and weight.
• We also need to identify the smallest living bird species.
• Options provide different pairs of birds such as ostrich, bee hummingbird, emu, house sparrow, albatross, pigeon, penguin, and bulbul.
• We assume the question refers to currently extant birds, not extinct species like the elephant bird.

Concept / Approach:
In zoology, the common ostrich is widely recognised as the largest living bird in terms of height and mass. At the other end of the scale, the bee hummingbird, found mainly in Cuba, is accepted as the smallest living bird, with extremely low body weight and tiny length. Knowing these two extremes allows us to scan the options and choose the pair that correctly combines them.

Step-by-Step Solution:
Step 1: Recall that the largest living bird is the ostrich, which can be over 2 metres tall and weighs more than 100 kilograms. Step 2: Recall that the smallest living bird is the bee hummingbird, which is only a few centimetres long and weighs just a couple of grams. Step 3: Examine the options to find which pair mentions both ostrich and bee hummingbird together. Step 4: Option A lists “Ostrich and bee hummingbird,” which exactly matches the known largest and smallest birds. Step 5: Therefore, Option A is correct and the remaining pairs can be rejected.

Verification / Alternative check:
Biology references and zoology textbooks consistently list the ostrich (Struthio camelus) as the world's largest bird and the bee hummingbird (Mellisuga helenae) as the smallest. Emus, albatrosses, penguins, sparrows, pigeons, and bulbuls are all significant or common birds, but none match the extremes of size represented by ostriches and bee hummingbirds. These facts are stable and widely agreed on in scientific literature.

Why Other Options Are Wrong:
Emu and house sparrow: The emu is large but smaller than the ostrich, and the house sparrow is not the smallest bird species.
Albatross and pigeon: Albatrosses are large seabirds, but again not the largest overall, while pigeons are mid-sized and not the smallest birds.
Penguin and bulbul: Penguins vary in size and some are tall, but the emperor penguin does not exceed the ostrich, and bulbuls are medium-sized songbirds, not the smallest.

Common Pitfalls:
Students sometimes confuse “large wingspan” with “largest bird” and may think of albatrosses, which indeed have one of the greatest wingspans. Others may choose very familiar small birds like sparrows as the smallest without checking scientific facts. It is important to distinguish between overall body size and just wingspan, and to recall that hummingbirds include the tiniest birds in the world.

Final Answer:
Thus, the correct pair is Ostrich and bee hummingbird.