问题如下：
Consider an ETF with the following trading costs and management fees:
● Annual management fee of 0.40%
● Round-trip trading commissions of 0.55%
●Bid–offer spread of 0.20% on purchase and sale
Excluding compound effects, the expected total holding-period cost for investing in the ETF over a nine-month holding period is closest to:
选项：
A. 1.05%
B. 1.15%
C. 1.25%
解释：
A is correct. The expected total holding-period cost for investing in the ETF over a nine-month holding period is calculated as follows: Total holding-period cost = Annual management fee + Round-trip trading commissions + Bid–offer spread on purchase/sale. Total holding-period cost = (9/12) × (0.40%) + 0.55% + 0.20% =1.05%.
哪里体现了买入卖出的整个过程，使得spread要用完整的bid ask spread
