opt in

基本解释

For example, we may share geographic location with application providers when you opt in to their location services.
比如比如，当用户选择使用苹果的位置服务的时候，苹果有可能会和应用提供者分享用户地理信息。
This must be a service that customers opt in to — and only after they are provided full information about the fees and the penalties they will incur.
该服务必须由客户选择加入，并且只能在向他们提供了充分的费用以及将承担的罚款信息之后。
He did, however, have to activate the app on her phone without her knowlege first. The service is 'opt in', so friends have to agree to 'watch' one another.
首先他没有经过妻子允许就进入了这个在妻子手机中的应用程式，所以朋友不得不同意进行视频。

If you decide to opt in by a pass fail, I just need to sign your white study card or if you wanna decide before the 5th Monday, just grab the pink slip and I can sign that and you can turn that in at any point and I'm happy to chat during break today or after class if you have any questions or concerns.
如果你上我们的课程只是要一个分数，那么我只需要在你的白卡片上签个名就可以了,或者说，如果在第五周的周一前还没考虑好，把你的解聘书拿来，只要我签个字,任何时候你都开以离开我的教室,当然，如果你有任何问题和疑虑,我也很高心和大家做课下交流。
哈佛公开课 - 计算机科学课程节选

But consumers can opt in or out of the service, and this anyway misses the point.
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We demand the right to Opt In before you manipulate the content we see.
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Benz blogs twice a week but only people who opt in receive the blog.
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