理论上来说，最好的防晒霜的防晒系数也就最高。

Theoretically, the best sunscreen has the highest SPF number.

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即使她从头到脚涂抹上防晒系数是7的防晒霜，她也会被晒伤。

She gets sunburned even when she plasters herself from head to toe in factor 7 sun lotion.

《柯林斯英汉双解大词典》

在我的皮肤科医生的建议下，我每天都会在脸上和脖子上涂上防晒系数为 15 或 30 的防晒霜。

For everyday, at my dermatologist's recommendation, I wear a sunscreen of SPF 15 or 30 on my face and neck.

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