Question

1) I heard him say that...
Please explain the grammar rules for "say" (present tense) after the word "heard".
2) A Economic Development Board survey...
Why is it "a" not "an"? Is it because it is "a survey"?
3) A historic moment...
I have seen some books writing "an historic moment"? It should be "a", isn't it?

Answer 1

1) I heard him say that...
Please explain the grammar rules for "say" (present tense) after the word "heard".
<b>It looks like an infinitive form without the defining "to" -- in this case the infinitive would be modifying the direct object "him."</b>

2) A Economic Development Board survey...
Why is it "a" not "an"? Is it because it is "a survey"?
<b>This is an error. It should be "An..."</b>

3) A historic moment...
I have seen some books writing "an historic moment"? It should be "a", isn't it?
<b>Some people do; others don't:
http://owl.english.purdue.edu/owl/resource/540/01/
Scroll down and read "Remember, using a or an ..."</b>