Which of the following describes a study that is “longitudinal”? A study that follows people for an extended period of time to see if they develop a disease or condition. A study that looks at people in one location, to reduce any bias introduced by varying locations. A study that follows people taking a drug or placebo for 6 weeks to see if they develop a disease or condition. A study that follows people taking medication in different locations, to see if their location impacts the medication’s effectiveness.

I'd say it's the first option, A study that follows people for an extended period of time to see if they develop a disease or condition.

Explanation:

warm front forms when a moist, warm air mass slides up and over a cold air mass. as the warm air mass rises, it condenses into a broad area of clouds. a warm front brings gentle rain or light snow, followed by warmer, milder weather.

hope i !

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.