Suppose that we compute a 90% z confidence interval for an unknown population mean μ, which of the following is a correcet interpretation? 。The probability that μ is in this interval is 90%. 90% of all possible z confidence intervals computed from samples of the same size would contain μ. 。The probability that μ is in this interval is 10%.

The confidence interval is build around the point-estimate of the true parameter.
Confidence interval interprets the chances for the true population parameter lies in it.
For example : A 95% confidence interval interprets that a person can be 95% sure that the true population parameter lies in it.

If we compute a 90% z confidence interval for an unknown population mean μ, then the correct interpretation would be :

A person can be 90% sure that the μ lies in it.

i.e. The probability that μ is in this interval is 90%.

Hence, the correct answer is "The probability that μ is in this interval is 90%."