Choose the option to replace the highlighted sentence: He is sleeping when I called him. 

Explanation:

📌 Problem in given sentence:

“He is sleeping when I called him.” ❌

👉 Error:

• “is sleeping” → Present Continuous
• “called” → Past Simple

➡️ Tense mismatch (present + past together ❌)

✔️ Correct Rule:

When one action is in progress in the past and another action interrupts it:

👉 Use:

• Past Continuous (ongoing action)
• Simple Past (interrupting action)

🧠 Structure:

Subject + was/were + V-ing + when + subject + V2

✔️ Applied:

• was sleeping → ongoing action ✔️
• called → interrupting action ✔️

❌ Why other options are wrong?

• has been sleeping ❌ → Present Perfect Continuous (not suitable with past “called”)
• is slept ❌ → grammatically incorrect
• has slept ❌ → Present Perfect (doesn’t fit with past “called”)

💡 Extra Examples:

• I was studying when she arrived.
• They were playing when it started raining.

⚡ Quick Tip:

👉 “when” + past action
➡️ Use Past Continuous + Simple Past

✅ Correct answer:

👉 was sleeping when I called