Select the most appropriate option to fill in the blank.

What a lovely smell! Mother _________ a cake. 

The correct answer is 'is baking'.

 Key Points

• The exclamation "What a lovely smell!" indicates a present experience, suggesting that the activity causing the smell is ongoing.
• The use of the present continuous tense "is baking" appropriately captures the current activity and is the best fit in this context.
• The sentence aims to convey a present action based on current evidence (the smell), making "is baking" the right choice.

Therefore, the correct answer is Option 4.

 Additional Information

• Option 1 ('had baked') would indicate a past action which doesn't fit the context.
• Option 2 ('bakes') is in simple present and typically describes habitual actions, not something happening right now.
• Option 3 ('will bake') indicates a future action which is not suitable given the current smell.