Step 1: Read the question.
Under the Indian Penal Code, 1860, we must find the situation in which the right of private defence of the body extends to even causing the death of the attacker.
Step 2: Know the law.
The right of private defence is given in Sections 96 to 106 of the IPC. Usually the law allows only reasonable force. But Section 100 lists special situations where this right extends to voluntarily causing the death of the attacker.
Step 3: Recall what Section 100 covers.
Section 100 allows causing death when there is a reasonable fear of death, grievous hurt, rape, unnatural lust, kidnapping or abduction, or wrongful confinement in a way that makes it impossible to seek help from the authorities.
Step 4: Test each option.
Option (A), an assault with the intention of kidnapping or abducting a person, is expressly covered by Section 100. Option (B), theft of property over 10,000, does not by itself justify causing death. Option (C), criminal trespass on open vacant land, does not justify deadly force. Option (D), a simple assault without a weapon, does not create the grave danger Section 100 needs.
Step 5: Give the reason.
Kidnapping or abduction is a serious threat to personal liberty. The law treats it as grave enough to allow deadly force in self-defence.
Step 6: Conclude.
So the right extends to causing death where the assault is committed with the intention of kidnapping or abducting a person.
\[ \boxed{\text{An assault committed with the specific intention of kidnapping or abducting a person}} \]