1. Geologists use physical properties to identify minerals. For example, the blank cleavage, color, fracture, hardness, luster, specific, gravity, streak, texture

The correct answer is - crystal form (external shape).

Explanation:

Physical properties are used for the identification of the minerals that include specific gravity, streak, texture, luster color, hardness, cleavage, and crystal form.

The most common physical property of the minerals in crystal form or external shape of the mineral. This is the property of the mineral that gives an idea about the homogenous possessing a 3-D internal order.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.