Choose the option that is the passive form of the sentence.

The security guard opened the gate using his pass.

The gate was opened by the security guard using his pass.

The correct option that is the passive form of the sentence is The gate was opened by the security guard using his pass.

The other options are incorrect because:

• The gate opened the security guard using his pass is in the active voice.
• The gate was open by the security guard use his pass is grammatically incorrect. The verb "to open" is followed by a past participle, but the word "open" is not a past participle.
• The gate is open by the security guard by using his pass is grammatically incorrect. The preposition "by" should be followed by a noun or a pronoun, but the phrase "by using his pass" is not a noun or a pronoun.