yes...most etf are duplicate from the most share choice from index

but garp 2009 practice states they are non-synchronous

题目：
4. You are asked by your boss to estimate the exposure of a hedge fund to the S&P 500. Though the fund claims to mark to market weekly, it does not do so and marks to market once a month. The fund also does not tell investors that it simply holds an Exchange Traded Fund (ETF) that is indexed to the S&P 500. Because of the claims of the hedge fund, you decide to estimate the market exposure by regressing weekly returns of the fund on the weekly return of the S&P 500. Which of the following correctly describes a property of your regression estimates?
a. The intercept of your regression will be positive, showing that the fund has positive alpha when estimated using an OLS regression.
b. The beta will be misestimated because hedge fund exposures are nonlinear.
c. The beta of your regression will be one because the fund holds the S&P 500.
d. The beta of your regression will be zero because the fund returns are not synchronous with the S&P 500 returns.

the answer provided by Garp is A,

cos
The alpha is spurious and results from the fact that returns are non-synchronous. d. is incorrect because the true exposure is linear. The beta is greater than zero and less than one because of non-sychroneity.

ETF本身应该说是和MARKET同步的（一般来说ETF应该是10秒刷新一次市值，所以来说还是很同步市场的），但是这个题目问的应该是HEDGE FUND自身，而不是HEDGE FUND所持有的ETF（题目中的应该investors持有HEDGE FUND,而HEDGE FUND又持有EFT来进行PASSIVE INVESTMENT)