Which of the following chemical compounds is the main component of natural gas?

With reference to sweet crude oil and sour crude oil, consider the following statements: I. Sweet crude contains comparatively less sulphur and is generally easier and less expensive to refine. II. Sour crude contains a higher proportion of sulphur compounds and therefore requires additional treatment to reduce corrosion risks and meet environmental norms. Which of the statements given above is/are correct?

Consider the following statements regarding Piped Natural Gas (PNG) and Liquefied Petroleum Gas (LPG): I. PNG is predominantly methane-based, whereas LPG mainly consists of propane and butane. II. Under ordinary conditions, PNG tends to be lighter than air, whereas LPG vapour is generally heavier than air. III. On a volumetric basis, LPG ordinarily has a higher calorific value than PNG. Which of the statements given above are correct?