How to get all options in a drop-down list by Selenium webdriver

<TD>
  <select name = "time_zone">
    <option value "-09:00"><script>timezone.Alaska</script></option>
    <option value "+00:00"><script>timezone.England</script></option>
    <option value "+02:00"><script>timezone.Greece</script></option>
    <option value "+05:30"><script>timezone.India</script></option>
  </select>
<TD>


IWebElement elem = driver.FindElement(By.XPath("//select[@name='time_zone']"));
List<IWebElement> options = elem.FindElements(By.TagName("option"));