White gold is primarily made from gold. However, pure gold is too weak to be used in jewelry, so it`s alloyed with other metals to enhance its durability.

Option 1 is the correct answer. White gold is often alloyed with nickel and palladium. Nickel adds strength and durability, while palladium gives it a whiter color.

Option 2 is not correct because cobalt is not commonly used in the making of white gold.

Option 3 is also incorrect. Although platinum and titanium are used in jewelry making, they are not typically alloyed with gold to create white gold.

Option 4 is incorrect because magnesium is not used in white gold. It could make the alloy brittle and consequently unsuitable for making jewelry.

In all options, it’s the presence of gold that is constant, with the varying other metals determining the color outcome, durability, and other physical properties of the resulting alloy.