In base-4, valid digits are 0, 1, 2, and 3. Therefore, 123 is valid, while 234, 345, and 456 contain digits not allowed in base-4.

A number is divisible by 10 if it ends in 0.

All listed methods are valid techniques for solving systems of linear equations.

All listed methods are valid for solving systems of linear equations.

In base 8, 15 is represented as '17' (1*8 + 7).

Machinery is considered a fixed resource as it does not change with the level of output in the short term, making option 2 correct.

Spherical geometry is an example of non-Euclidean geometry, where the usual rules of Euclidean geometry do not apply.

All of the options listed are valid constraints that can be applied to a set of integers, thus making 'All of the above' the correct answer.

Each of the options listed represents a valid constraint that can be applied to a set of integers.

A hybrid set can contain elements of different types, such as numbers, strings, and floats, as seen in {1, 'apple', 2.5}.

The equation y = x^2 - 4 is non-linear because it involves a variable raised to a power greater than one.

Group problem-solving exercises are designed to enhance collaboration and strengthen relationships among team members, making them a key component of team-building activities.

√2 is an irrational number because it cannot be expressed as a fraction of two integers.

Since 1000 is 10^3, log_10(1000) equals 3.

'Censorship' is often associated with limiting freedom of expression, which contradicts democratic principles, while the others support democracy.

Overconsumption is contrary to sustainability, while the others promote sustainable practices.

'Algorithm' is a term used in mathematics and computer science, while the others are core concepts in psychology.

'Symphony' is unrelated to environmental issues, while the others are directly connected to global warming.

Reduced communication is not a benefit of team formation; in fact, effective teams thrive on enhanced communication to achieve their goals.

Reduced communication is a drawback, as effective teams thrive on open dialogue and information sharing.

A Fibonacci sequence cannot be expressed as a linear function; it is defined recursively.

In a geometric progression, the terms are numeric and follow a specific ratio; thus, non-numeric terms do not fit the definition.

In a geometric sequence, the ratio between consecutive terms is constant, not the difference.

In a geometric series, the ratio between consecutive terms is constant, not the difference.

A regular polygon is defined as a polygon with all sides and angles equal, and it cannot be concave; it must be convex.

An effective team thrives on feedback, so a lack of feedback is not a characteristic of an effective team.

Frequent conflicts without resolution is NOT a characteristic of high-performing teams, as they typically manage conflicts constructively.

Hybrid sets can include duplicate elements, especially when they are formed from multiple sources.

Multiples can be both odd and even; hence, they are not always odd.

The graph of a quadratic function is a parabola, not a straight line.