Questions with the keyword 'respiration'

• why can I only hold my breath under water for 30 seconds? by mac2003 to Andrew, Bruce, Lindy, Lizzie Comments: (so far, 2s comments )
• why do we breath out carbon dioxide ? by lulu8 to Andrew, Bruce, Lindy, Lizzie Comments: (No comments so far )
• why do we breathe out carbon dioxide by tach13 to Andrew, Bruce, Lindy, Lizzie Comments: (so far, 2s comments )