Approximately how many brain cells are present at birth?

• A. 100 billion
• B. 1 million
• C. 10 trillion
• D. 50 billion

Answer: (A)

The main idea being tested is how many brain cells are present at birth. It’s commonly taught that a newborn’s brain contains about one hundred billion neurons. This reflects that most neurons are already in place before birth, and what follows is a rapid expansion in connections rather than a large increase in neuron numbers. The reason this figure fits best is that it aligns with standard developmental neuroscience data showing that early brain growth relies on wiring up existing neurons through synapses and pruning, not on producing vastly more neurons. Claims of far fewer neurons would not support the newborn’s basic neural activity, while numbers far above this estimate don’t match typical measurements of birth counts.