关于英国公平人寿保险的问题请教-经管之家官网！

请问各位大侠，这个当年使英国公平人寿保险陷入困境的产品是什么意思呢？
Between 1957 and 1988, the Equitable sold thousands and thousands of retirement savings policies with built-in guarantees.
How did these policies work ?
The policyholder paid premiums which were invested by the life office. Each year, reversionary bonuses were declared. At the date of maturity, the life office would also declare a substantial terminal bonus. The policyholder would then have a choice:
(a) to convert the accumulated sum to an annuity using the guaranteed annuity rates specified in the policy;
(b) to take this sum and use it to purchase an annuity at the market rates applying at the date of maturity.
For many years, there was no problem. The market rates were always higher than the guaranteed rates, so the policyholders always chose the second alternative. But in the 1990s, interest rates fell and life expectancies increased. By September 1998, the guaranteed rates were about 25% higher than the market rates.
看不懂这个产品给policyholder两个选择究竟是什么意思。
谢谢大家帮帮忙