71.   If the valve is parallel to the pipe, the gas is on.

72.   If the principal gas was carbon dioxide, Mars could have developed greenhouse conditions to retain atmospheric heat and maintain a relatively warm climate.

73.   If there is enough oxygen for a fuel to burn completely, the gas produced is carbon dioxide, which is not toxic.

74.   If you plan on grilling after work or want to grill your breakfast, gas is the way to go.

75.   In addition, gas is easily stored, while electricity must be used as it is generated.

76.   In any case, experts said that a gas like sarin is particularly effective in enclosed places like subways or tunnels, where it cannot rise and dissipate.

77.   In certain concentrations, hydrogen sulfide gas can be toxic to bottom-dwelling fish and other creatures.

78.   In the far-off reaches of this New Europe, unleaded gas was even more a rarity than it was in Italy.

79.   In winter, there was no gas.

80.   Invisible and scentless, the suffocating gas is one of the reasons miners would want to bring a canary with them.