Concept:
Imperative sentences in active voice are generally changed into passive voice using the structure:
\[
\text{Let + object + be + past participle}
\]
Step 1: Identify the sentence type.
"Give up smoking" is an imperative sentence expressing a command or advice.
Step 2: Apply the passive voice rule.
\[
\text{Give up smoking}
\]
becomes
\[
\text{Let smoking be given up}
\]
Step 3: Verify the options.
• Smoking may be given up -- changes the meaning.
• He gave up smoking -- active voice.
• Let smoking be given up -- correct passive form.
• Let smoking be gave up -- incorrect grammar.
\[
\boxed{\text{Let smoking be given up}}
\]