To solve this problem, we need to understand the structure of natural rubber.$\newline$Natural rubber is a polymer of isoprene (2-methyl-1,3-butadiene).$\newline$The polymerization of isoprene units in natural rubber occurs in a specific configuration.$\newline$Let's analyze the options:$\newline$• Option 1: All cis-configuration.$\newline$• Option 2: All trans-configuration.$\newline$• Option 3: Alternate cis- and trans-configuration.$\newline$• Option 4: Random cis- and trans-configuration.$\newline$Natural rubber predominantly consists of polyisoprene chains with a cis-configuration.$\newline$This means that the double bonds in the polymer chain are in the cis-configuration.$\newline$Therefore, the correct answer is Option 1: All cis-configuration.