Cov kev qhia tawm, xws li cov kab hluav taws xob tawm suab, lub pob ntsia hlau, thiab cov lus qhia hla cov menyuam, yog cov khoom siv tseem ceeb hauv ntau qhov kev lag luam, kom ntseeg tau meej thiab du. Txhawm rau tswj lawv lub neej ntev thiab kev ua haujlwm, lubrication kom zoo yog qhov tseem ceeb. Hauv tsab xov xwm no, peb yuav e...
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