Q1: The specific weight of water is 1000 kg/m3

ANS:D - all the above.

The specific weight of water is 1000 kg/m³ at 4°C temperature. The specific weight of a substance is the weight per unit volume. For water, at 4°C, its density is 1000 kg/m³, which means 1000 kilograms of water occupies 1 cubic meter of space. This value is considered standard for the density of water and is independent of external factors such as pressure or location. While water's specific weight remains constant under varying pressure conditions and mean sea level, its temperature affects its density, which in turn influences its specific weight. At 4°C, water has its highest density, which results in a specific weight of 1000 kg/m³. Therefore, the correct statement is: at 4°C temperature.