It’s really ______ exciting experience to go on a trip into ______ space.

A an, /          B an , the      C the , /          D the , the

体积相同的实心木球和实心铝球，浸没在水中时，它们受到的浮力______（选填“相等”或“不相等”）；如果换成质量相同的实心木球和实心铝球，浸没在水中时，______（选填“木球”或“铝球”）受到的浮力大．