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1. Predict the output of this program. ``

cpp
#include <iostream>
#include <string>
using namespace std;

string check(int n) {
    if (n < 0) {
        return "negative";
    }
    if (n > 10) {
        return "big";
    }
    return "small";
}

int main() {
    cout << check(-3) << " " << check(12) << " " << check(4) << "\n";
}

``

negative small smallnegative big smallnegative big bigsmall big small

2. Predict the output of this program. ``

cpp
#include <iostream>
using namespace std;

int main() {
    cout << boolalpha;
    int age = 17;
    bool has_id = true;
    cout << !(age >= 18 && has_id) << " " << (age < 18 && !has_id) << "\n";
}

``

false falsetrue truefalse truetrue false

3. This guard is meant to refuse an amount that is zero or negative. What is the bug? ``

cpp
string check_amount(int amount) {
    if (amount > 0) {
        return "amount must be positive";
    }
    return "ok";
}

``

The test is backwards: it refuses 5 and accepts -5, so the test should be amount <= 0The return type should be bool, not stringThe guard should come after the return "ok" lineNothing is wrong; the guard works as written

4. A student wants to refuse a person who is under 18. What is the bug? ``

cpp
int age = 16;
if (!age >= 18) {
    cout << "refused\n";
}

``

The if needs braces around the conditionThe >= should be <=, so the test checks the upper limitThe ! applies only to age, so the test compares !age (0 or 1) with 18; write !(age >= 18) or age < 18The message needs endl instead of \n

5. True or false: for a double x, !(x < 1.0) and x >= 1.0 always give the same answer.

True, because < and >= are opposite tests for every double valueFalse, because a NaN value makes both < and >= false, so !(x < 1.0) can be true while x >= 1.0 is false

Guards and De Morgan