All Free Biology MCQs with Answers

781. Which statement about hookah or shisha smoking is correct?

• A. It is safer than cigarettes because the smoke passes through water
• B. It also delivers nicotine, tar and carbon monoxide and is harmful
• C. It contains no tobacco at all
• D. It affects only the mouth

Explanation: The water cools the smoke but removes little tar or CO, and sessions are long, so intake is substantial. The belief that the water filters out harm is the myth this question tests.

782. The most effective way to reduce smoking related disease in a population is

• A. treating lung cancer at an earlier stage
• B. giving antibiotics to all smokers
• C. preventing people from starting and supporting smokers to quit
• D. switching smokers to cigars

Explanation: Emphysema and cancer are largely irreversible once established, so prevention and cessation save far more lives than treatment of late disease. Cigars carry the same tobacco harms.

783. The hardness of bone is due to the deposition of

• A. salts of calcium, such as calcium phosphate
• B. silica particles
• C. sodium chloride crystals
• D. chitin fibres

Explanation: Bone combines a flexible framework of collagen with hard calcium salts, giving both strength and a little spring. Without the mineral component bone would bend, and without collagen it would shatter, which is why both parts matter.

784. The number of pairs of true ribs in the human body is

• A. 5
• B. 7
• C. 10
• D. 12

Explanation: Of the twelve pairs of ribs, the first seven attach directly to the sternum by their own cartilages and are called true ribs. The next three pairs are false ribs sharing cartilage, and the last two are floating ribs with no front attachment.

785. The human skull is made up of how many bones?

• A. 14
• B. 16
• C. 22
• D. 29

Explanation: Eight cranial bones enclose the brain and fourteen facial bones form the face, giving 22 in all. Most are fused at immovable sutures, the only freely movable bone being the mandible.

786. The number of thoracic vertebrae in the human vertebral column is

• A. 5
• B. 7
• C. 4
• D. 12

Explanation: The column has 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and 4 fused coccygeal vertebrae. The twelve thoracic vertebrae each carry a pair of ribs, which helps fix the number in memory.

787. The pectoral girdle of the human body is composed of the

• A. clavicle and scapula
• B. femur and tibia
• C. radius and ulna
• D. sternum and ribs

Explanation: Each half of the pectoral girdle is a clavicle plus a scapula, and the arm bones attach at the shoulder socket. The pelvic girdle, in contrast, is formed by the hip bones joining the sacrum.

788. The only freely movable bone of the skull is the

• A. maxilla
• B. mandible
• C. nasal bone
• D. zygomatic bone

Explanation: The mandible hinges at the temporomandibular joint, allowing chewing and speech, while every other skull bone is locked to its neighbours by sutures. The maxilla is the fixed upper jaw.

789. When the arm is bent at the elbow, the biceps contracts while the triceps

• A. contracts at the same time
• B. contracts even more strongly
• C. relaxes
• D. detaches from the bone

Explanation: Muscles can only pull, so the flexor biceps and the extensor triceps work as antagonists: one contracts while the other relaxes, and they swap roles when the arm is straightened. Both contracting together would lock the joint.

790. Skeletal muscles are attached to the bones they move by

• A. ligaments
• B. cartilage
• C. synovial fluid
• D. tendons

Explanation: Tendons are cords of tough collagen that tie muscle to bone and transmit the pull of contraction. Ligaments join bone to bone across a joint, and mixing these two up is one of the commonest slips in anatomy.