A parent reports that his 2-year-old child often fails when running. The nurse interprets this as indicating which of the following as a normal aspect of a toddler’s vision

A. Near-sightedness.
B. Far-sightedness.
C. Binocular vision.
D. Strabismus.

蒸汽系统暖管时，暖管速度无须控制，只要达到规定温度即可。