Select the word that best fits the definition: economic activity characterized by fluctuating levels of growth and decline
a. job security
b. interest rate
c. economy
d. business cycle

Business cycle

Explanation:

The business cycle can be known as economic cycle is the cycle in which the gross domestic product can be seen moving in upward and downward direction.

The length of this cycle is the period in which consists of single boom and contraction sequence.

It shows the fluctuating levels of growth and decline in the economy.

i'm pretty sure it's spores

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation: