either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration.
Most babies first pull themselves up to a standing position between about eight months and 10 months. At this stage your baby will need to hang on to you or a solid piece of furniture. By 11 months she may be able to stand on her own.
The first stages of sitting is when baby still stabilizes herself by pressing on the floor. What this information says is that at age 7 months, roughly 70% of all babies can sit alone for short periods of up to about half a minute.