Step 1: Definition of zero coupon bonds.
Zero coupon bonds are debt securities that do not pay periodic interest payments. Instead, they are issued at a deep discount to their face value and mature at par value.
Step 2: Features of zero coupon bonds.
These bonds are issued at a zero rate of interest, meaning the investor does not receive any regular interest payments, but instead, the interest is accumulated in the form of a capital gain at maturity.
Step 3: Conclusion.
Thus, the correct answer is (A) At zero rate of interest.
Final Answer:
\[
\boxed{\text{At zero rate of interest}}
\]