Present perferct tense

[mneeti]

Hi, it might sound silly what I am going to ask, please bear with me.

I was looking at the example given on page 107 of the Manhattan guide 7 and I am stuck at one point.

Present perfect tense:

Sentence 1: This country HAS ENFORCED strict immigration laws for 30 years.

According to the guide, the sentence means that "this country enforced law in the past and still enforces them today"

I understand this sentence in 2 ways: 1) above, as per the guide is correct
2) The country did enforce the law in the past for any 30 years and may or may not still be continuing to do so. What I am trying to say here is that, isn't the second meaning of the sentence to state the eternal fact that happened in the past and still holds true? Please help me with the second meaning.

Sentence 2: They HAVE KNOWN each other since 1987.

How is the meaning of the above sentence different from: They know each other since 1987.

Can simple tense be used here in place of present perfect? If not, what is the reason.

Thank you in advance for your input on the meaning, I now find present perfect tenses a bit confusing.

[RonPurewal]

Questions about strategy guide material belong in the MGMAT non-CAT folder. Please re-post your query there.

Thanks.