Answer
$4\ metric\ tons$
Work Step by Step
Since a truck can haul very heavy loads, the appropriate measuring unit is $metric\ tons$. That is, my uncle’s new truck can haul a load of $4\ metric\ tons$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.