One of these substances is a liquid at room temperature. which one? one of these substances is a liquid at room temperature. which one? sih4 co2 nh2oh cf4

Those compounds are said to be liquids at room temperature whose melting point is less than 25 °C and boiling point is greater than 25 °C.

Silane:  (SiH₄)

                      Melting Point  =  -185 °C

                      Boiling Point  =  -112 °C

Carbon Dioxide:  (CO₂)

                      Melting Point  =  -56.6 °C (Triple Point)

Hydroxylamine:  (NH₂OH)

                      Melting Point  =  33 °C

                      Boiling Point  =  58 °C

Tetrafluoromethane:  (CF₄)

                      Melting Point  =  -183.6 °C

                      Boiling Point  =  -127.8 °C

Result:
           Hence, it can be concluded that none of the given compound is in liquid state at Room temperature. But, approximately speaking we can conclude that comparatively if the day is hot then Hydroxyl Amine (NH₂OH) will exist in liquid state. :)